[dragonwriter]

> Are you familiar with U.S. elections?

Yes. Intimately.

> Caucuses are very much part of the primaries. They are how certain states perform their primaries.

No, caucuses are a (formerly, universally used—primaries are a newer thing) alternative to primaries still used in a minority of states (and sometimes, by some parties but not others in a state) to select delegates to Presidential nominating conventions.

Because primaries have over time displaced caucuses as the main candidate selection mechanism, and because the campaigns are somewhat nationalized, and because there isn't a handy name for the whole process, the whole national process of selecting such delegates is sometimes sloppily referred to as “the primary” of each party.