AAC audio file: This is a standard AAC (Advanced Audio Coding) file. It can be created by the iTunes built-in AAC encoder.
Matched AAC audio file: This is a standard AAC audio file, downloaded from an iCloud account, using iTunes Match.
MPEG audio file: This is a standard MP3 file. It can be created by using the iTunes built-in MP3 encoder.
Protected AAC audio file: This is the default filetype for songs purchased from the iTunes Store prior to the introduction of the DRM-free iTunes Plus format in April 2009. The DRM built into the file prevents it from being copied/shared beyond the iTunes account it’s associated with.
Purchased AAC audio file: This is the default filetype for songs purchased at the iTunes Store after April 2009. The Purchased AAC audio file format no longer has the DRM-based copy restrictions.
