Last October, the Staples Center was filled with hundreds of thousands of passionate fans, though not the type you would expect in the storied sports arena.

The fans that sold-out the stadium in an hour weren't there to watch Game 7 of the NBA Finals. They were there to watch professional gamers compete on the international stage at the World Championships of the video game League of Legends — one of the largest and most watched eSports tournaments in history.

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Since then, League of Legends eSports (the term for professional gaming) has continued to grow in popularity, but, more importantly, in legitimacy. As Riot Games' professional league — the League Championship Series (LCS) — enters the second half of its second season, it's all beginning to look more and more like traditional sports.

The league has salaried players who are recognized by the U.S. State Department as professional athletes and a Fantasy League where fans can draft gamers like an NFL fan would draft Peyton Manning or Tom Brady.

The LCS made League of Legends one of the most accessible eSports in the Western world, but just how did it happen and how do you even play it? With the second half of the its second season starting on Tuesday, now’s a better time than any to get acquainted with how this all works.

What’s the game even about?

League of Legends, which Riot Games released in 2009, is a Multiplayer Online Battle Arena, or MOBA. Since then, it has become one of the most-played video games in the world with 27 million people playing daily.

The game, nuanced and strategic, pits teams of five players against each other to destroy the enemy team’s Nexus, a hexagonal power structure and the main objective of the game. Each team picks five champions out of more than 100 to strategically flank and counter their enemy in a virtual war on a map called Summoner's Rift.

Before the match begins, players pick their team's five champions in a draft phase; each team bans three champions from their opponent to strategically isolate certain players. Then, in alternating turns, teams pick their champions, each of which has a specific purpose and position on the map.

A map of Summoner's Rift from the video game League of Legends designates the map positions and key objectives of the game. Image: Riot Games

The five team roles, named according to map position, are the Top Laner, Mid Laner, Jungler, AD Carry and Support. A typical League of Legends game, which lasts around 30 to 40 minutes, has three phases characterized by different jobs for each role.

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In the early game, the Support player starts in the bottom lane with the AD Carry — the most fragile member of the team — and protects him; in the late game, the Support concentrates more on controlling key, tactical positions on the map. In the mid and late game, the Mid Laner and AD Carry do the most damage, so they try and battle the enemy team with their teammates.

How does the league work? If you know anything about traditional sports, the LCS will sound familiar.

You start with a regular season

Eight teams in the European league (EU LCS) and the North American league (NA LCS) compete in weekly matches for standing that will eventually determine playoff seeding. The regular season is split into two 11-week seasons known as the Spring Split and the Summer Split.

Professional LCS team Cloud 9 prepares to play Team SoloMid in the Summer Split Grand Finals in Santa Monica, Calif. on Sept. 1, 2013. Image: Flickr, Vincent Samaco

Then you move on to playoffs

At the end of every split, the top six teams according to regular season standings compete in a single-elimination playoff tournament that determines the final split standings and which teams will compete at international events. The first- and second-seed teams get first-round byes and the remaining four teams compete in the quarter finals.

Fan favorite Team SoloMid celebrates after defeating rival team Counter Logic Gaming to advance to the Grand Finals of the Summer Split Playoffs in Santa Monica, Calif. on Aug. 31, 2013. Image: Flickr, Vincent Samaco

And if you're one of the best, you head to the World Championships

While being at the top of your region is great, true glory comes from being the best in the world. Because international events are few and far between, the teams put everything on the line to qualify for the opportunity to test their mental and mechanical skill with the best of the best.

That happens in October, when the top three teams from North America, Europe, South Korea, China and Southeast Asia compete for the title of world champion and millions of dollars in prize money.

Asia has, historically, dominated the World Championships. Southeast Asia's Taipei Assassins took the title and $1 million at the Season 2 World Championships in 2012. South Korea's SK Telecom T1 K won the Season 3 World Championships and $1 million at the Staples Center last year.

The South Korean team has become synonymous with victory. After winning in L.A., the team went back to compete in the winter season of South Korea's Champions league — regarded as the most competitive league in all of League of Legends eSports — and won without dropping a single game.

Visitors cheer for international teams during the All-Star tournament of the computer game 'League of Legends' on May 8, 2014 in Paris. Image: Getty Images/AFP/Lionel Bonaventure

The Champions league has only become more competitive and other South Korean teams have since dethroned the SK Telecom T1 K gods, who have been in a slump as of late. Though "slumping" for a South Korean team means going to the 2014 All-Stars Tournament in Paris earlier in May and winning the entire tournament — again, without dropping a game.

While history favors the South Korean teams, both the North American and European regions are facing the fiercest competition they have seen thus far in their respective regions. That means they could make a splash on the international scene this year — but only the best teams will make it to the World Championships in South Korea.

All the LCS action that leads up to that most important event is broadcast weekly on Riot Games' League of Legends eSports site. If you truly love sports and all that it entails — competition, teamwork, striving for excellence — there's no reason to discount this league just because it's behind a computer screen and not on a field. Let the games begin.