Wow, this topic actually isn't covered by the FAQ section on top. Anyways, it just means schools will review your application as they receive it so the earlier you get your stuff in, the better your chances (b/c more seats still available).
This is different vs schools who have set deadlines and are NOT on rolling admissions. For example, school A might have a deadline of Nov 1, so they review all of its app's at the same time. This means a person who finishes their app's on Oct 20 has the same chance of getting in as someone who finished June 1st.
