Apple Computers developed this audio format to store very high quality audio. It stands for Audio Interchange File Format.
The format can store mono, stereo and even multi-channel audio that is normally used in soundtracks.
The format was developed in 1988 in accordance with Electronic Arts Interchange File Format (IFF) standards. All AIFF files will therefore have an .aif or .ief extension.
Another feature that differentiates AIFF from other audio containers is that AIFF files are uncompressed, meaning the files hold the highest quality but are much larger in size, then say, an MP3 file.
There is a variety of the format, termed AIFF-C, which supports compression algorithms of about 6:1. They are compressed thus losing some of the full quality of the normal AIFF, but the difference is hardly noticeable.
The format was originally designed for Mac computers but the format can now be read by PCs with Windows as well. It is the same way Macs can read Microsoft's WAV files, another uncompressed audio format. Despite that fact AIFF files are very popular among Mac users and audio professionals such as record labels while PC users stick with WAV.