FLAC means Free Lossless Audio Codec. As the name suggests, this is an audio file format that still maintains the quality of the original (such as a CD track). Unlike lossy formats which are the parts of the audio stream to produce small file sizes, compression, FLAC does not sacrifice the quality of sound and can also almost half the size of the file. In the past, this codec is typically used for backup to CD. However, with large capacity hard drives and high-speed Internet connections are becoming more common, FLAC is now also used for daily listening, and live audio streaming.
Even the advantages of flac format, there are some situations where you want to convert it to another audio codec. For example, even on mobile devices sized things, and you can almost twice as FLAC files to MP3 files on a portable music player. So, while FLAC is well supported by most software and hardware players, in some cases, you will have no choice but to use another popular codec like MP3 or WMA.