Flac stands for free lossless audio codec. grossly oversimplified, flac is similar to mp3, but lossless. the flac project consists of:

* the stream format
* libflac, which implements a reference encoder, stream decoder, and file
decoder
* flac, which is a command-line wrapper around libflac to encode and decode
.flac files
* input plugins for various music players (winamp, xmms, and more in the
works)
this package contains the api documentation for all the flac libraries.