Studio album: A collection of songs recorded in a studio and released, for the first time, as a single entity. It must be at least 25-30 minutes long, but most tend to be 40-60 minutes.
EP: An "extended play," meaning a release longer than a single (but not as long as an album).
Single: A particular song (often with 1-3 bonus "b-side" tracks) released to promote an artist or album. Successful singles become chart hits.
Live album: An album-length recording made in front of an audience, usually a concert performance.
Compilation: A collection of recordings that have been previously released in another form, or that were not originally intended to be released together.
Mixtape: A semi-official promotional album (this category is not intended for personal mixtapes made among friends).
Remix Album: A collection of remixes of previously released tracks.
Soundtrack: A release recorded specifically for a TV or movie soundtrack.
Bootleg: An unauthorized release.
Karaoke: A release intended to accompany karaoke performance.
Interview: A release featuring interviews with an artist.
Unknown: None of the above.