Non rolling schools will have a uniform acceptance date at the end of the application process where all offers will go out. Thus, while sending in your application early may get an earlier review, it will not help your chances of getting an "early acceptance." There are a few "semi-rolling schools" that have a few acceptance dates throughout the process and make offers at those points, and only those points.
Rolling admissions are basically first come-first served (except for those they put on hold and review at a later date). If a favorable decision is made on your file, you'll hear from them soon.
It is my understanding that both types of admission procedures can give you waitlists. Non-rolling admissions simply offer the chance to be evaluated with everyone else in the applicant pool, not just those that happened to apply at the same time you did.
At least, this is my understanding of the topic.... =)