Starting in January this year and running through June, every state in the nation will hold either a primary or caucus to nominate delegates to represent their candidates at the national party conventions this summer.

Although both are used to select delegates, primaries and caucuses are extremely different. Caucuses used to be the most commonly used process, but primaries have taken over as the preferred method in the last several decades.

Caucus

Caucuses are meetings held statewide in high schools and town halls and are open to all registered voters of the party. In some caucuses, like Iowa's, independent voters are allowed to participate as well.

Rules for caucuses vary state by state and party by party, but generally the voters divide themselves up into groups according to the candidate they support, and the undecided voters also gather in a group and prepare to be swayed by the groups that have a preferred candidate. Representatives of each group then give speeches in hopes of persuading others to join their group.

At the end of the process, the number of voters in each group is counted to determine how many delegates will represent each candidate at the county convention, and then the state convention, at which delegates are chosen to attend the party's national convention.

The whole process takes several hours, and because of the time commitment required, fewer voters typically participate in caucuses than primaries. The shift from caucuses to primaries began in 1968 with the McGovern-Fraser Commission, which was created in response to the chaos and rioting that happened at the 1968 Democratic Convention in Chicago.

The commission was formed in part to ensure a more transparent process by which party leaders select delegates, and the end result was most states switched over to primaries to simplify the process and make complying with all the new rules and regulations easier.

Primary

Like the caucuses, primaries are open to all registered members of the party holding the primary, and some states also allow independent voters to participate.

The primary is not much different than voting in a general election as voters simply show up at polling stations and cast their votes by secret ballot for their preferred candidate, which will determine how many delegates the candidate will have representing them at the national convention.

Rules for primaries vary by state, and there is no universal process used.