What is the difference between a Ballot and a Signup and an Exam/Quiz?

They are the same in nearly every way.

The ballot is a "secret" ballot system. No one has access to the details of the ballot submissions. Depending on options selected, administrators of the ballot may be able to see a list of who has submitted a ballot (but, again, not thier choices). The option selected will be shown on the ballot.

The signup is much like the ballot except that the administrators can see the details of the submissions....who selected what.

The quiz/exam allows you toenter a "correct" answer and will generate a % correct score.