How does the delegate system work for primaries?

[J. J.]

It also varies from party to party.  In PA, the Democrats have "pledged" delegates.  If you want vote for Obama, you have to vote for a candidate chosen by Obama who is bound to vote for her.  They are elected by congressional district and each each district gets a minimum number, plus a number based on how the last Presidential Nominee of the Democrats did in the last election.  The super delegates, e.g. the congressional delegation, the Governor, and state chair, are delegates ex officio.

In the GOP, each district gets 3 delegates, Plus a number based on the presidential vote in the district; they are unpledged in PA, meaning that they can use their own judgment.  They also have super delegates.

In Iowa, the regular delegates are elected by a state convention, which is composed by delegates elected at the county convention, which is elected by delegates elected at the precinct level (the caucuses).  I think they have super delegates too.