What is the difference between a Primary Election and a Caucus?

In the US voting system, there are two rounds of voting generally every two and four years. First, a primary or a caucus is held. During those, voters pick a party nominee. For example, in a Democratic primary, voters (often but not necessarily registered as Democrats) would pick among Democratic candidates for an office. The winner of that election then goes on to run in the general election against the nominees of the other parties. Caucuses are not primaries. During a presidential caucus, state political party supporters gather to elect delegates to represent them at a state presidential nominating convention. These in-person gatherings can last for hours and involve intense negotiations as people try to convince one another of their preferred candidate’s merits. A primary is organized by states, not political parties. Rather than requiring participants to gather in one place at one time, a primary is an election. Depending on the state, voters either choose candidates directly or select delegates who will represent their preferred candidate in a statewide party convention, a process known as an indirect primary.