What is the Iowa caucus, and who gets to vote?

Answer 1

It's the primary in Iowa. Iowans are eligible to vote.

Answer 2

In the Iowa caucus, the Iowa people gather together at a special location, discussion regarding the candidates, and then vote.

The whole process may take up to 3 hrs. Although all Iowa people can vote, many cannot find 3 hrs to do so, and they include the hospital doctors, old folks, etc. And, because it requires discussion, it does not allow absentee balot (voting) as permissble in a primary (e.g., in new hampshire).