Audio Interchange File Format (AIFF)
aiff stands for audio interchange file format
Not the same! A song in a commercial CD usually/ normally was stored in an AIFF format. If you imported/ converted this song into an AAC format, then there will be some quality lost. And, if you then export/ convert this song (from AAC format into AIFF), that lost part is never be regained; the later AIFF song is not the same with the first(original) one.
For digital formats, an uncompressed format, such as WAVE or AIFF is best.
wav and aiff
AIFF means Auto Interchange File Format used in the Apple Macintosh operating system. It is a file for storing audio digital sound data
MP3, WAV, AAC, Apple Lossless, MPEG4, AIFF
Wave, AIFF SND and many other formats are not compressed. Most of these are variations of a PCM (pulse code modulation) format.
MP3, AIFF, WAV, MPEG-4, AAC and Apple Lossless (.m4a) including QuickTime's supported files.
The music is stored on a CD as AIFF audio files. If a CD icon appears you can usually double click it and drag the files into your Music folder. AIFF files are relatively large and so are often converted to the MP3 format to save space. A typical song will be around 20MB (AIFF) which will be reduced to around 4MB (MP3). Free software, such as iTunes or numerous others, will recognise the CD and convert the music to MP3s, or whatever format you prefer, and help manage the Music folder.
The iPod can take songs from anywhere if they are in the right format. The supported formats include AAC, MP3, Audible, AIFF, and WAV.
You can play songs from anywhere on an iPod Touch providing they are in a suitable format - AAC , MP3, Audible, Apple Lossless, AIFF or WAV. These can be from the iTunes store, Amazon, or any other retailer with a download service, or from your own CD collection. Tracks from CDs are in the AIFF format which takes up a lot of space on your iPod but the iTunes software can convert these to the more compact MP3 or AAC formats.
Both iTunes and Garageband will convert WAV of AIFF files to MP3 format. Each of these are free on a Mac platform. I don't know if they are free for PCs.