The U.S. women's soccer team has had a well-publicized fight for equal pay since winning this summer's World Cup. But the battle with U.S. Soccer and FIFA started well before fans broke out in chants of "Equal pay!" at the team's ticker-tape parade in New York City in July.

What is the story behind the USWNT's fight for equal pay? How do other sports match up? What has happened since the World Cup? Here is a primer on one of the biggest topics in sports right now -- which we will continue to update as more news happens:

What's been happening?

On August 14, mediation talks broke down between the USSF and the women's soccer team, with a spokesperson for the players saying they "eagerly look forward to a jury trial."

The two sides met in New York for several days but could not reach any formal agreement.

On Aug. 19, District Judge R. Gary Klausner set a trial date for the lawsuit brought against U.S. Soccer by members of the women's national team (more on this below). The trial will begin May 5, 2020, and last four to five days.

Then on Nov. 8, a judge granted the players' motion to be certified as a class action lawsuit -- a win for the players. The players' spokesperson for the lawsuit, Molly Levinson, called it "a historic step forward in the struggle to achieve equal pay." Levinson added, in a statement: "We are so pleased the Court has recognized USSF's ongoing discrimination against women players -- rejecting USSF's tired arguments that women must work twice as hard and accept lesser working conditions to get paid same as men."

The class designation awards the players injunctive relief for any player who is a team member on the day of final judgment or appeal, as well as back pay and punitive damages for any player on the team at any time between Feb. 4, 2014, and the present.

Things have continued to be contentious between the two sides since the conclusion of the World Cup. In July, U.S. Soccer president Carlos Cordeiro released a letter that claimed the federation has paid the female players more than the men in recent years. Cordeiro's letter details analysis -- which he says was conducted by his staff and reviewed by an accounting firm -- that shows that U.S. Soccer paid female players $34.1 million in salaries and game bonuses from 2010 to '18 and paid male players $26.4 million in the same period.

However, there was some murkiness because of the differences in the compensation structures for the men's and women's teams. What's more, salaries in the National Women's Soccer League were factored in to the calculations. Levinson called the letter "a sad attempt by USSF to quell the overwhelming tide of support the USWNT has received from everyone from fans to sponsors to the United States Congress."

The U.S. men's team issued a statement in support of the USWNT, saying, "The members of the United States National Soccer Team Players Association once again stands with the members of the world champion Women's National Team in their pursuit of fair compensation for their work as professional soccer players. The USMNT players were not impressed with US Soccer Federation president Carlos Cordeiro's letter made public on Monday. The Federation downplays contributions to the sport when it suits them. This is more of the same."

How did the USWNT get here?

The equal pay battle didn't begin around the World Cup, but it was heightened by the event. The U.S. women have been fighting for equality for some time. In 2016, five high-profile members of the USWNT -- Carli Lloyd, Hope Solo, Alex Morgan, Rapinoe and Becky Sauerbrunn -- filed a complaint against the United States Soccer Federation (commonly referred to as U.S. Soccer) with the Equal Employment Opportunity Commission. The EEOC never issued a decision on the case, and in the meantime, the women signed a new collective bargaining agreement with the USSF. In August last year, Solo filed her own case against U.S. Soccer -- with similar complaints -- in a personal lawsuit, which remains pending in California.

Things ramped up this year. On March 8 -- not coincidentally, International Women's Day -- 28 members of the USWNT filed a lawsuit against U.S. Soccer accusing it of gender discrimination. The complaint was filed in California district court and argued that U.S. Soccer "has a policy and practice of discriminating" against members of the women's national team on the basis of gender. The lawsuit contends that the USSF is in violation of two federal laws: the Equal Pay Act and Title VII of the Civil Rights Act of 1964.

The U.S. women's team has been far more successful on the international stage than the men's team. This World Cup win was the women's fourth. The men's best finish came in 1930, when the team placed third. The men didn't qualify for the 2018 World Cup, yet compensation does not reflect each team's performance.

The U.S. women's current lawsuit contends that if the men's and women's teams won each of the 20 non-tournament games they are contractually required to play, women's team players would each earn a maximum of $99,000 ($4,950 per game), and men's team players would earn $263,320 ($13,166 per game). The suit also states that from 2013 to 2016, women players earned $15,000 for making the national team, and the men earned $55,000 in 2014 and $68,750 in 2018. (In response to this, U.S. Soccer told ESPN that these figures were pulled from the old collective bargaining agreement, and a new one was signed in 2017.)

Were the "equal pay" chants directed at U.S. Soccer?

They were most likely directed at both U.S. Soccer and FIFA, the world governing body of soccer, which puts on the World Cup.

FIFA awarded $30 million in prize money for this year's women's tournament. The 2018 men's tournament had $400 million in prize money. Although FIFA president Gianni Infantino has said he wants to double the prize money for the women's tournament by 2023, the gap between the genders could grow, with FIFA expected to award $440 million for the men's tournament in 2022.

FIFA's position on prize money is that it's tied to revenue. Simply, the men's tournament brings in much more than the women's. Some projections of what the tournaments earn in revenue have been made public, but not all of the numbers are available. (The New York Times reported projections of $6.1 billion for the 2018 men's tournament, and FIFA projected the Women's World Cup would bring in $131 million over the four-year cycle.) This raises the question of whether it's fair to cut prize money proportionately. FIFA has the funds to close the gap; the organization's cash reserves hit a record $2.74 billion in 2018.

Many women's players have also expressed frustrations about institutional favoritism toward men. One example they point to: FIFA's decision to schedule two men's tournament finals (the Copa America men's final and the CONCACAF Gold Cup men's final) on the day of the Women's World Cup final. Said Megan Rapinoe on the eve of the title game, "If you really care, are you letting the gap grow? Are you scheduling three finals on the same day? No, you're not. Are you letting federations have their teams play two games in the four years between each tournament? No, you're not. That's what I mean about the level of care. You need attention and detail and the best minds that we have in the women's game helping it grow every single day."

Are there issues besides money outlined in the USWNT lawsuit?

Yes. The USWNT has also fought for better conditions. The women had lesser accommodations while traveling and routinely had to play on artificial turf instead of natural grass, which is kinder to the body.

According to the complaint, between Jan. 1, 2014, and Dec. 31, 2017, the USWNT played 62 domestic matches, 13 (21%) of which were played on artificial surfaces. During that same period, the USMNT played 49 domestic matches, only one (2%) of which was played on an artificial surface. (Since the lawsuit was filed, U.S. Soccer has scheduled all of the women's games on natural grass.)

As for travel, the lawsuit states that in 2017, the men's team flew on chartered flights on at least 17 occasions, and the women did not have a chartered flight that year. In response, U.S. Soccer told ESPN that 2017 was the final year of qualifying for the men's team prior to the 2018 World Cup, and therefore most of the flights were chartered for a competitive advantage. The organization said it has consistently offered the same travel accommodations for the men's and women's teams.

Chants of "equal pay" broke out at the USWNT's victory parade in New York City. Getty

What is keeping U.S. Soccer from paying the women's team equal salaries?

It's a bit complicated. The men and women both have negotiated separate collective bargaining agreements with the USSF. (The women's current contract runs through 2021.) The biggest difference is pay structure. The men receive much higher bonuses when they play for the national team. The women receive guaranteed salaries (about $100,000 a year), but their bonuses are much smaller. The women haven't necessarily complained about their pay structure -- after all, this is what they negotiated -- but they want their fair share of the money being doled out. The lawsuit contends that "the USSF has never offered female WNT players pay at least equal to the pay afforded to male MNT players."

The USSF's formal response to the lawsuit claimed that any differences in pay are "based on differences in the aggregate revenue generated by the different teams and/or any other factor other than sex."

But let's talk about that money. Where does it come from? The biggest revenue streams are TV deals, sponsorship deals and ticket sales. It's tricky to decipher how much the men are bringing in with TV deals and sponsorship deals versus the women because those deals are often sold in bundles. When it comes to ticket sales, the women have actually earned more over the past three years, according to audited financial statements obtained by The Wall Street Journal.

From 2016 to 2018, women's games generated approximately $50.8 million in revenue, compared to $49.9 million for men's games. Here's the sneaky caveat: The men average higher attendance, but the women have played more games, which leads to more revenue. The women have also done more promotional and media tours than the men in that span.

What is a potential solution?

There is one outlined in the lawsuit: The WNTPA proposed a revenue-sharing model to "test the USSF's 'market realities' theory." In that model, player compensation would be directly linked to how much revenue each team generates.

What else have the men said about it?

The U.S. men's team issued a statement in support of the women's lawsuit and the revenue-sharing model.

It read: "The United States National Soccer Team Players Association fully supports the efforts of the US Women's National Team Players to achieve equal pay. Specifically, we are committed to the concept of a revenue-sharing model to address the US Soccer Federation's 'market realities' and find a way towards fair compensation."

Has everyone been supportive of the issue?

In short, no. In July, 2014 World Cup team member Jermaine Jones ignited controversy when he said in a video interview posted on the website TooFab, "The girls, I appreciate everything they're doing, they're doing an amazing job, but of course, as men, we know it's tougher to win a World Cup than the girls." He later went on to say, "I think they have to be careful too because you have players [like] Alex Morgan, they are making more than some of the guys, but then they scream out and say, 'We need more money.' ... It can backfire real quick."

In an interview with The Guardian published on Tuesday, Aug. 13, Atlanta United manager Frank de Boer said he does not believe in equal pay.

"I think, for me, it's ridiculous," he said. "It's the same like tennis. If there are watching, for the World Cup final, 500 million people or something like that, and 100 million for a women's final, that's a difference. So it's not the same. And of course they have to be paid what they deserve to [earn] and not less, just what they really deserve. If it's just as popular as the men, they will get it because the income and the advertising will go into that. But it's not like that, so why do they have to earn the same? I think it's ridiculous. I don't understand that."

(De Boer later said he regretted those remarks, especially the use of the word "ridiculous.")

Can anyone else step in?

Some politicians are trying. U.S. Senators Jacky Rosen, D-Nev., and Amy Klobuchar, D-Minn., wrote a letter to the Senate Commerce Committee in July calling for a hearing "on the significant issue of pay disparity between men's and women's sports in the United States."

The letter stated: "As you know, this Committee has previously held hearings on issues within its jurisdiction over sports matters, including hearings on combating sexual abuse in Olympic sports and preventing opioid abuse among athletes in the previous Congress.

"Following the USWNT's latest World Cup victory, a hearing would afford a timely opportunity for the Committee to recognize the importance of protecting and empowering athletes -- while also examining the troubling pay disparities that have been highlighted in recent weeks."

Does pay inequity spill over to other women's professional sports?

Yes. Hockey is perhaps the best recent example. Ahead of the 2017 IIHF World Championships, the U.S. women's national team threatened to boycott as a protest against USA Hockey, citing stalled negotiations for "fair wages and equitable support" from its governing body.

The players and USA Hockey ended up agreeing to a landmark, four-year agreement just before the tournament, ending the holdout (and the chance that USA Hockey would put out a replacement squad for the tournament). The team's annual compensation improved to roughly $70,000 per player, plus performance bonuses that could push their incomes over six figures if they win the Olympics or world championships. USA Hockey also agreed to other player asks, such as establishing a committee to look into how the federation could improve its marketing, scheduling, public relations efforts and promotion of the women's game, plus fundraising and other efforts for girls' developmental teams.

The U.S. women's hockey team won gold at the 2018 Olympics, less than a year after threatening to boycott the 2017 world championships due to wage and other inequalities. Ken Murray/Icon Sportswire

While men can earn millions of dollars in the NBA, NHL or soccer leagues, few will be surprised to hear that the same opportunities don't exist in women's professional sports. Differences in sponsorships, ticket sales and TV rights, among other things, contribute to big disparities in pay between men's and women's pro leagues.

Although the NWSL -- the longest-running professional women's soccer league in North America -- increased its roster size and salary cap for this upcoming season (a positive sign), its salaries pale in comparison to figures we see in men's soccer. The 2019 NWSL salary cap is $421,500, with the minimum player salary $16,538 and the maximum player salary $46,200. The MLS Players Association lists salaries on its website: The lowest-paid players for 2019 make $56,250, and the highest-paid player is Zlatan Ibrahimovic at $7.2 million.

Frustration over salaries and quality of life concerns were principal reasons WNBA players opted out of their collective bargaining agreement last year. (That means the current agreement will end after the 2019 season, and both sides will have to negotiate a new one.) The current rookie minimum is $41,965, and the veteran maximum is $117,500 -- a fraction of their NBA counterparts' salaries. Players say they aren't expecting to make NBA salaries, but they don't think they're being paid what they're worth. Some players supplement their income by playing abroad in the offseason, though that carries inherent risks. Look no further than the costly injuries to Indiana Fever guard Victoria Vivians (torn ACL while playing in Israel) and reigning WNBA Finals MVP Breanna Stewart (ruptured Achilles while playing with her Russian club), who are both out for this WNBA season.

The women's professional hockey landscape is in even more upheaval. After the Canadian Women's Hockey League (CWHL) made the stunning decision to shutter after the 2018-19 season -- citing an "unsustainable business model" -- more than 200 women's hockey players announced they would not play in any league until there was a more viable option that included better benefits and more money. That led to a formation of a union, the Professional Women's Hockey Players Association, which features most of the top players in women's hockey, including Team USA's Hilary Knight, Kendall Coyne and Brianna Decker.

The PWHPA will go on a barnstorming tour this fall -- with confirmed dates already in Toronto, Chicago and New Hampshire -- to drum up fan interest and maintain their visibility. But players who participate in the tour, which will include exhibitions and meet-and-greets, will not be compensated.

There's still an existing league, the NWHL. Even though the NWHL promised a 50-50 cut from league sponsorship and media deals, salaries for those intending to play in 2019-20 range from about $5,000 to $12,000.

And the U.S. women's soccer team isn't the only team in the sport fighting against its own federation. Just two months after appearing in its first World Cup, the Jamaican women's team -- the Reggae Girlz -- has announced it will not train or compete until its players are paid. The Reggae Girlz claim the federation owes them money. Forward Khadija Shaw told the BBC: "Of course 100 percent we always want to represent our country. It's not just about the money, it's a stand that needs to be done. Hopefully this can be resolved as soon as possible and we can put this behind us and represent our country ... We are in a position where we are literally fighting just to get paid by legal agreements. [This is] about change, change in the way women football is viewed, especially in Jamaica."

The Reggae Girlz have been fighting for equality ever since 2010, when the Jamaican Football Federation cut their funding. They were unable to play for a period of time, and lost their FIFA ranking.

In November, the Football Federation Australia and the players' association announced a landmark deal that would see Australia's women's senior international team earn as much has their male counterparts, according to the Daily Telegraph. The women's and men's teams will reportedly share 40% of commercial revenue and prize money evenly; historically, the men's team was allocated a greater share of the commercial revenue and was paid more to play.

Could sponsors and brands step in and help level the playing field?

Adidas announced in March that it would be paying its athletes on the winning World Cup team the same performance bonus payments that would be owed to their male counterparts. (Adidas does not disclose the amount of its bonuses.)

In April, LUNA Bar made a $718,750 donation to the USWNT Players Association, with the stipulation that the money be used to pay the 23 members of the 2019 World Cup team. The figure was calculated to make up the $31,250 per player difference in bonuses given to men and women for making the World Cup roster.

Secret Deodorant (through parent company Procter & Gamble) did something similar after the World Cup, announcing (via a full-page ad in The New York Times) that it would donate $529,000 -- or $23,000 for each of the 23 players to help close the pay gap.

There are plenty of other examples. However, experts in the industry say that while the boost and exposure are nice, brand involvement historically hasn't leveled the playing field.

Jayna Hefford, who served as commissioner of the CWHL last season before it folded, said that while it shows a "sound corporate responsibility that might resonate with consumers," she learned to understand that "company mandates are to make money and run a business," so it has to be a partnership that makes sense. While Hefford stressed that women's hockey players aren't expecting NHL salaries -- echoing the WNBA players -- it is difficult to count on sponsors to keep the league afloat.

Val Ackerman, the first president of the WNBA, said that traditionally, sponsors don't dictate how that money is spent. For instance, a sponsor isn't saying, "Here's $500,000, but it must be allocated to player salaries." Rather, the money goes into a general revenue pot, and the owner or commissioner can view at as an additional revenue stream from which to draw. Running a league costs tens of millions of dollars -- more than brands are usually willing to spend. What's more, it's not sponsorships that bring in the big bucks, but rather TV deals that have raised the profiles of leagues such as the NBA, NHL, NFL and MLB.

What happens next?

We'll wait and see. No new mediation is currently scheduled, but a letter to U.S. Soccer officials dated Aug. 12 and signed by the 28 players involved in the suit says in part:

"While we are prepared to take our equal pay fight through a trial if necessary, we believe that both sides would benefit from an equal pay and equal working conditions settlement now."

It's also to be determined if politicians in Washington step up with hearings and what might come from that. What is clear: This conversation isn't going away.

"All players, I'm saying every player at this World Cup, put on the most incredible show that you could ever ask for," Rapinoe said. "We can't do anything more to impress, to be better ambassadors, to take on more, to play better, to do anything. It's time to move that conversation forward to the next step."