I think you're mixing up two formats: Apple Lossless and AAC. Apple Lossless (or ALAC) is very similar to FLAC and is (of course) a lossless format. When you rip a CD in Apple Lossless is will be bit perfect af decompressing, just like FLAC. I have ripped all our CDs in Apple Lossless. I could convert all the files to FLAC if needed or to WAV or AIFF. I can burn CDs from ALAC files and they will sound exactly the same as the ripped CD.
https://en.wikipedia.org/wiki/Apple_Lossless
AAC is similar to mp3 and is a lossy format. One of the problems with ALAC and AAC is that they use the same file extension: m4a. Without analysing the file it is impossible to know whether the file is in a lossless or a lossy format. That's why bootlegging sites don't like it.
https://en.wikipedia.org/wiki/MPEG-4_Part_14#.MP4_versus_.M4A