The eyes of the nation will be fixated on Iowa on Feb. 3, as the state’s caucuses kick off the presidential nominating calendar.

This raises the perennial question: What exactly is a caucus and how does it work?

Tens of thousands of Iowans will gather on the night of the first Monday in February at caucus sites – known as precincts – across the state, in what will be the first contest in the wide open and wild race for the Democratic presidential nomination.

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But unlike a primary – which is a traditional "one person, one vote" election – there is no casting of ballots in a caucus.

While the number of caucuses has edged down in recent years, nine states and three U.S. territories still hold them. And two of the first three states that hold contests in the nominating calendar – Iowa and Nevada – are caucus states.

In Iowa, the action will take place at 1,679 precincts across the state – which will be held in school gymnasiums, church basements, union halls, community centers, libraries or any other place where people can gather. The action kicks off at 7 p.m. Central Standard Time – with the caucuses normally lasting from one to two hours, depending on the size of the caucus.

This year, there’s a new twist. Iowa Democrats who can’t make it to their local caucus site will be able to take part at one of an additional 987 additional satellite caucuses across the state, the country, and the globe. These new satellite caucuses will take place at factories, firehouses, group homes or community gathering places. The new option should help shift workers, Iowans with disabilities and those serving overseas take part.

Only registered Democrats are allowed to take part in the Democratic caucuses. Seventeen-year-olds can caucus if they turn 18 by November’s general election.

Forty-one pledged delegates to the Democratic National Convention are up for grabs in Iowa — and the monthslong process to choose them starts on the night of the caucuses.

In 2008, 239,872 Democrats turned out to caucus in Iowa — which was nearly 40 percent of registered Democrats in the state. Turnout dropped in the 2016 Democratic caucuses to just 171,109 — less than 30 percent of Iowa’s registered Democrats.

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Here’s how all the action plays out:

-There's a call to order.

-A caucus chair and secretary are elected by the crowd.

-A representative from each campaign can get up and make a final case for the candidate they are backing.

-Caucusgoers separate into groups in corners or parts of the room for their candidates of choice.

-After the groups are formed, the person elected chair of the caucus adds up how many supporters are for each candidate.

-Each candidate has to meet a threshold of 15 percent to be considered viable. That means the number of people backing a candidate has to be at least 15 percent of the total number of people in the room at the local caucus. For example, if there are 100 people in the room and 14 are backing a particular candidate, that candidate is not considered viable.

-If a candidate is determined to be not viable, that contender’s supporters need to support another candidate. During the "re-caucusing" process, supporters from the remaining viable candidates try to encourage those who were supporting the non-viable candidates to come their way.

-After the re-caucusing process is over, the final numbers are tallied. The number of people in each viable group will factor into how many delegates each candidate wins from that precinct. Delegates are awarded proportionately – and the number of delegates a candidate has statewide will be reported as "state delegate equivalents." The candidate with the most "state delegate equivalents" will be considered the winner of the caucuses.

-But wait, there’s more. For the first time, the Iowa Democratic Party will also announce the popular vote from the first round of caucus results – before the realignment from the "re-caucusing" process. If a candidate who didn’t win the traditional "state delegate equivalent" count captures the first-round popular vote, this could allow for multiple candidates to claim they came out on top in Iowa.