From iA wiki
Acronym: Free Lossless Audio Codec
A lossless, open-source, patent-free audio compression tool and audio format. It does not discard any audio data, unlike lossy formats such as Ogg Vorbis, MP3, and WMA. FLAC was developed to give users true CD-quality audio but its file size is much larger than lossy formats: about 50% the original file size compared approximately 1/10th the original size of comparable lossy formats. FLAC is similar to Monkey Audio but without the license restrictions / issues. GPL and LGPL license distribution.