The race for the Democratic presidential nomination officially begins Monday with the Iowa caucuses. Tens of thousands of Iowa Democrats are expected to turn out to determine who wins the first-in-the-nation contest after an exhaustive campaign season that began two years ago.

If you're looking for a refresher on how the caucuses work, or perhaps planning to caucus for the first time, we've put together a step-by-step look at the process, which has changed significantly since 2016.

What is a caucus, anyway?

Unlike a primary, a caucus is not a "one person, one vote" system. Instead, Iowans will be electing delegates through a complex process that dates back to the 19th century. There are no ballots, and caucus-goers aren't technically voting for candidates but rather for delegates who support a given candidate.

Caucus-goers elect these delegates by moving around a room. If you support one candidate, you move to one part of the room. If you support another candidate, you go somewhere else.

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If this all sounds strange and antiquated to you, you're not alone. The national Democratic Party has been trying to limit the number of caucuses in recent years in favor of straightforward primaries, which mostly resemble any other election.

But Iowa, which fiercely defends its privileged status in the nominating calendar, has stood by its process and rejected talk of scrapping its caucuses, which in turn allows New Hampshire to hold the first formal primary just over a week later.

Now to the nitty-gritty of how this whole thing works.

Where and when will people caucus?

Much like a typical election, where you caucus is based on your address. That caucus location is known as a precinct.

There are 1,678 precincts across Iowa. They include school gymnasiums, church basements, union halls, community centers, libraries or really any place a group of people can gather.

The caucuses will take place at 7 p.m. CT on Monday, February 3. The presidential preference portion of the night, which is when caucus-goers elect delegates for one candidate or another, will likely take an hour or two depending on the size of the precinct.

There will also be "satellite caucuses" that will be open to the general public for the first time in an effort to expand access. The idea is to allow people to participate who may not be able to leave a job or assisted living facility to caucus. It also gives some Iowa residents living outside of the state on caucus night to participate in caucuses.

In December, the Iowa Democrats announced there will be 99 satellite caucus sites, including 71 in Iowa, 25 in other states and three international sites in France, Scotland and the Republic of Georgia.

People participate in the Democratic caucus at the Iowa State Historical Society in Des Moines, Iowa February 1, 2016. Brian C. Frank/Reuters

Who is eligible to caucus?

In order to participate, you need to be a registered Democrat in Iowa. You do not need to show any form of identification at the caucuses, but you will need to sign an oath that says you are who you say you are and aren't caucusing twice. Seventeen-year-olds can caucus if they turn 18 by the general election in November.

If you're registered as a Democrat, you can show up at your precinct to check in or you can pre-register by January 17 with the state party to avoid standing in a longer line on caucus night. You can think of this like a TSA pre-check for the caucuses.

If you're not registered to vote by February 3, fear not, you are able to register at your precinct on caucus night. And if you are registered with another party, you are also able to register as a Democrat on caucus night at your precinct.

As you walk in the door, you'll be given a card to write your first choice candidate on one side, and your second choice candidate on another side. More on this in a moment.

The room where it happens

Once everyone is checked in and filed into the room, there will be some brief speeches from the people in charge of leading the caucus and local officials. Also, representatives from the campaigns can get up and speak in order to give a last-minute pitch to attendees.

Once those speeches wrap up, it's time for the presidential preference portion of the night to begin. Again, rather than checking a box on a ballot, each candidate will have an area of the room where supporters are supposed to gather. You would head to the designated area for your top choice to stand with fellow supporters.

And remember that card you were handed on your way in the door? You would also write down that candidate's name where it's listed on that card. That will give the state party a backup in case there needs to be any recounting.

After everyone is gathered in their candidate's area, the caucus leaders will count how many people are in each group. This is where things get a little funky.

The process

At this point, any candidate that has support from at least 15% of the caucus-goers in the room will have their supporters locked in. That 15% is known as the "viability threshold," which a candidate needs to hit in order to win delegates. So in a room with a 100 people in it, a candidate needs the support of at least 15 people to win delegates. (Note: In some smaller precincts, the viability threshold is higher, but the process works the same.)

If you are backing a viable candidate, then you are done moving around for the evening. If you are with a candidate who has 14 percent support or less in the room, you'll be participating in a process known as realignment. In previous years there were several rounds of realignment, but there will only be one round this year in an effort to speed the process up.

If you're involved in realignment, you have a few options: Join a viable candidate's group, convince other people from non-viable groups to support your candidate to hit the viability threshold, or go join another non-viable candidate other than the one you supported to hit the viability threshold. Alternatively, you could just go home. This realignment process is critical. If your candidate wasn't viable and you're looking for a new group, viable campaigns will be competing to try to win you over. If you're part of a well-organized campaign on the cusp of viability, your team will be desperately trying to try to pick off supporters of other non-viable campaigns. The best organized campaigns, with well-trained and experienced people on their side, are in strong positions to increase their size on caucus night.

Once you're with your final candidate's group, you would write the name of the candidate who you are supporting on the card you were handed when you walk in the door. This will again serve as a backup for the party.

How many people show up

In 2016, 171,109 people turned out to the Democratic caucus in what turned out to be a historically close race between former Secretary of State Hillary Clinton and Vermont Senator Bernie Sanders. That was about 29 percent of registered Democrats in the state.

In 2008 there was a huge turnout, and a record 239,872 Democrats turned out to caucus. That was nearly 40 percent of registered Democrats. In the 2004 race, 124,331 Democrats, or 23 percent of registered Democrats, turned out to caucus.

Turnout is difficult to predict, but many Iowa Democratic leaders project this could be the largest caucus ever. Former Iowa Democratic Congressman Dave Nagle said he wouldn't be surprised to see a record 250,000 people turn out this year.

"The intensity of interest this year is beyond what I've seen before," Nagle said. "You look at '08 and that was pretty good, but this seems to even gather more interest and more passion."

Why the caucuses matter

Iowa has a solid track record of picking Democratic presidential nominees. Since 1976, seven of the nine nominees, including the last four, have won the Iowa caucuses.

As we mentioned earlier, people on caucus night will technically be electing delegates, rather than a standard popular vote. Each precinct is assigned a number of delegates based on how many people there voted for previous Democratic candidates.

The number of people in each viable group after the realignment will determine how many delegates each candidate wins from that precinct. Those delegates will be awarded proportionally.

The delegate math

This is where it gets really tricky.

When the caucuses are over, the state calculates how those delegates from all 1,678 precincts equate to delegates sent to the county, congressional district, and state conventions. The number of state convention delegates a candidate has will be reported on caucus night as "state delegate equivalents."

That state delegate equivalent number determines how many of Iowa's 41 pledged national delegates are awarded to a candidate. The person with the most state delegate equivalents wins the Iowa caucuses because they end up with the most national delegates.

Those national delegates will then head to the Democratic National Convention, which will be held in Milwaukee this summer. In theory, the delegates a candidate wins will vote for them to become the nominee at the convention. In practice, this would only happen at a "brokered convention," which Democrats have managed to avoid since their 1968 convention descended into chaos.

In any event, Iowa's 41 delegates are only two percent of the 1,991 national delegates a candidate needs to win to secure the nomination. So the real prize out of Iowa isn't the delegates as much as it is momentum that comes from a strong finish in the contest.

This year, that state delegate equivalent will be the "main" number reported on caucus night, according to Iowa Democratic Party Chairman Troy Price, but it won't be the only one.

After 2016, the Democratic National Committee asked Iowa Democrats to also report the popular vote results from the first alignment. Price said the state party wanted to go a step further and will also release the results of the popular vote from the realignment to show how people moved around the room.

If a campaign wins the first round popular vote, but not the most state delegate equivalents, it could open the door to a campaign claiming a different type of victory, some strategists and longtime Democrats say.

"They could say, you know, we should be the winner because at the first division we were the winner," said longtime Iowa Democratic Strategist Jeff Link, referring to the case a campaign could make if they only win the popular vote on first alignment. He expects the realignment popular vote to be similar to the state delegate equivalents.

"The person with the most state delegate equivalents will be the campaign that not only started out in a strong position in a caucus but also was able to convince either uncommitted or unviable caucus tenders to join their side."