A provisional acceptance means that you can indicate that you want your applications to other universities (within the same discipline) to remain active. However, if you accept an offer for 1 discipline and receive an offer for a second, you must choose between the 2. You cannot hold 2 acceptances (firm or provisional) at 1 time.

A firm acceptance means that you will be removed from the wait lists of all other choices (in the same discipline) on your application.