Patch rpms?

Hi I've recently installed 8.0, my first try with SuSE and I'm very pleased with it, but notice that in at least one of the security update announcements there is a '.patch.rpm' as well as normal '.rpm' and '.source.rpm' files available for download. Could some kind soul please tell me what the '.patch' rpms are for, and do I need them and if so what should I do with them? TIA Pam