So basically all it does is check whether the file was downloaded properly? I should've made my original question more clear, how does it work in relation to mp3 files, as some sets that I've downloaded came with a .sfv file?
If you use an sfv checker, it will do a crc check of the files listed in the sfv and match the crc generated against the crc written in the file. If they match, then there has been no corruption of the file. If they don't match, then the file is corrupted or not complete, or something to that effect.