verify disk problems

What does this mean? and what should I do about it:

Verifying volume “Macintosh HD”
Checking HFS Plus volume.
Checking Extents Overflow file.
Checking Catalog file.
Checking multi-linked files.
Checking Catalog hierarchy.

Checking Extended Attributes file.
Checking volume bitmap.
Checking volume information.
Volume Header needs minor repair
The volume Macintosh HD needs to be repaired.

Error: The underlying task reported failure on exit


1 HFS volume checked
Volume needs repair


Every time I verify the disk it unexpectedly fails so it won't let me repair disk