AIFF (acronym for Audio Interchange File Format) is an audio format created for handling high-quality audio data for computers and electronic devices.
Mainly used on the Macintosh platform, AIFF is a lossless and uncompressed format, that provides support for streaming several audio tracks from a computer to an app.
Using more disk space than MP3 files, AIFF is widely used by professional audio and video software applications. AIFF audio files can be currently played using most audio players.
Moreover, AIFF players will usually allow their users to build their own custom playlists that will also contain tracks of other formats, besides the AIFF ones.