Stands for "Audio Interchange File Format." AIFF is a file format designed to store audio data. It was developed by Apple Computer, but is based on Electronic Arts' IFF (Interchange File Format), a container format originally used on Amiga systems.
A standard AIFF file contains 2 channels of uncompressed stereo audio with a sample size of 16 bits, recorded at a sampling rate of 44.1 kilohertz. This is also known as "CD-quality audio," since CDs use the same audio specifications. AIFF audio takes up just over 10MB per minute of audio, which means a 4 minute song saved as an AIFF will require just over 40MB of disk space. This is nearly identical to a .WAV file (which uses the same sample size and sampling rate as an AIFF file. However, it is about ten times the size of a similar MP3 file recorded at 128 kbps, or five times the size of an MP3 file recorded at 256 kbps.
Since compressed and uncompressed audio files sound nearly the same, most digital audio distributed over the Internet is saved in a compressed format, such as an .MP3 or .M4A file. This makes downloading audio from websites or the iTunes Store much faster and more efficient. However, AIFF files are still commonly used for audio recording, since it is important to save the original audio data in an uncompressed format. By working with uncompressed AIFF files, audio engineers can ensure that the sound quality is maintained throughout the mixing and mastering process. Once the final version of a song or other audio project is saved, it can then be exported in a compressed format.
NOTE: While the standard AIFF format does not support compressed audio data, Apple developed a variation of the AIFF format, called AIFF-C, which supports audio compression. This format is also based on the original IFF format, but includes extra space in the file structure to define the type of the compression. Therefore, the AIFF-C format can store audio generated from multiple compression algorithms.