CNN  — 

In November, Americans will once again be filling out ballots to decide who will lead the country for the next four years. These ballots will have a single presidential candidate for each of the major parties, selected earlier in the year by a series of primary elections held in each state. On January 15, Iowa Republicans will kick off the season by holding their version of a primary election – the Iowa caucuses.

Iowa has traditionally been the first state every four years to hold a presidential nominating contest of any kind. Here’s how votes at the Iowa caucuses will help determine the Republican Party’s choice for a presidential candidate:

Can anyone go to a caucus?

Just like with primary elections, some states allow voters to come regardless of party affiliation, some require you to have been a registered party member beforehand, and some use a mix of the two. Iowa Republicans, for example, allow you to sign up to become a party member on the night of the caucuses. Check with your state’s party organization to find out how it will work for you.

Is a caucus the same as a primary?

Yes and no. A caucus is put on by a political party as part of the presidential nominating process, but it’s not exactly the same as a primary election. Primary elections are held throughout the day and always use a private ballot. While the form caucuses take varies from state to state, caucuses are typically held at a specific time and often give voters an opportunity to listen to prospective candidate representatives before registering support for their candidate of choice. In some states, voters organize themselves into groups supporting their candidate, thus making their selection known to others.

Why does Iowa matter?

Iowa represents the first major test of a campaign’s ability to communicate with voters on the national stage. As the first state in each cycle to have their primary, it catches candidates while their campaign funds are full and their energy is fresh. As a small state, Iowa also pitches itself as an opportunity for less well-funded candidates to have success campaigning on the ground. Despite the spotlight, the results of the Iowa caucuses have not consistently predicted who will eventually become the party’s nominee.

What are Democrats doing?

In past years, Iowa Democrats have held caucuses where voters physically split up into groups (sometimes multiple times) to indicate their support for a candidate. This year, Iowa Democrats will meet on January 15 to conduct party business; however, due to changes in the Democratic nominating calendar, they won’t vote for presidential candidates. Instead, that vote will take place by mail, ending on March 5.

CNN’s Ethan Cohen contributed to this story.