The audio data in most AIFF files is uncompressed pulse-code modulation (PCM).
For the compressed variants it is supposed to be .aifc, but .aiff or .aif are accepted as well by audio applications supporting the format.
With the development of the OS X operating system now known as macOS, Apple created a new type of AIFF which is, in effect, an alternative little-endian byte order format.
For the vast majority of users this technical situation is completely unnoticeable and irrelevant.
The sound quality of standard AIFF and AIFF-C/sowt are identical, and the data can be converted back and forth without loss.
Apple has also created another recent extension to the AIFF format in the form of Apple Loops[6] used by GarageBand and Logic Pro, which allows the inclusion of data for pitch and tempo shifting by an application in the more common variety, and MIDI-sequence data and references to GarageBand playback instruments in another variety.