FLAC files are lossless and can be as good as or better than CD quality but will not play in iTunes or Windows Media Player. You can read more about FLAC here.
-Please note that FLAC files cannot carry meta data, so you will not receive album art, track names, etc.

You will be able to play FLAC files in VLC Media Player, which you may safely download below:

Download VLC Media Player for Mac here.

Download VLC Media Player for PC here.