FLAC stands for free lossless Audio codex, which is an alternate kind of format for ripping a CD. The popular method is with MP3, while the less known is the FLAC. The major discrepancy between the MP3 and FLAC is basically in the way by which they perform the compression of audio information. MP3 is the flossy type of format where the part of the audio information which listeners are most likely not to hear is regarded as waste and thus discarded.
While FLAC, as the name suggests and implies, is lossless, which means that no information would be lost and every part of the audio information is retained, and none is lost. FLAC and MP3 also differ in the resulting size after the compression, though they are both small when compared to the original WAV, which is an uncompressed format. For instance, if the WAV file is around 40mb, the MP3 could be 4mb while FLAC is 20m.