Release Type : Single
A Single is a release that contains a single track only. It can also contain remixes or different versions of that 1 single track. If a different track is added to the release it becomes an EP.

Release Type : EP
An EP is a release that contains 2 - 8 tracks from 1 or multiple artists. It can also include remixes or different versions of those tracks.

Release Type : Album
An Album is a release that contains any of the following -
1. Over 45 minutes worth of music
2. A continuous DJ mix
3. 8 or more different tracks.