Basically, rolling admissions works by keeping you in the pool of applicants. Let's say you send in your application along with 100 other kids in December. The school looks at your application and decides that they don't really want you. Instead of sending you a rejection letter right off the bat, they "roll" you over until Jan. Then, they look at your application is comparison to the other Jan applicants. At this point the school can decide they like you or they can roll you over again until Feb. Rolling admission is good because the schools are suppose to look at your application every single round of applicants rather than simply throwing it out after one look at it.