Like its real world counterpart, a patch is a "make-do" fix rather than an elegant solution. Patches are sometimes ineffective, and can sometimes cause more problems than they fix. Patch management experts, such as Mark Allen, CTO of Gibraltar Software, suggest that system administrators take simple steps to avoid problems, such as performing backups and testing patches on non-critical systems prior to installations.
Patch management can be viewed as part of change management.
(This information courtesy of Whatis.com.)