Apple has posted a full guide, detailing how to use fsck.
Fsck is not a curse word, it’s the utility that modern UNIX-based operating systems use to verify the filesystem, and repair it when needed. In Mac OS X, when you click Verify Disk inside of Disk Utility, you’re actually running fsck. Now, Apple has a full guide showing how to take command of fsck, even if you’re an ordinary user.
I know to a lot of you this may be nothing new, but there are some intermediate users that could pick up a trick or two from the guide. And, novice users should also take a read… for that rare chance that the Mac gets sick. Apple worked on making the guide for all experience levels.