How to read a UUID to determine whether it’s supposed to be random, or has a specific meaning. Where you’ll find them, and whether you’ll ever see two the same.
GUID
Where would you find a 7C3457EF-0000-11AA-AA11-00306543ECAC? How UUIDs have taken over to identify so much, and how to generate your own.
Accessing information about you as a user and a great deal more, using the Advanced Options dialog for user accounts, and Directory Utility.
They’re almost everywhere now: UUIDs and GUIDs identify disk volumes, printers, even the processes running on your Mac. Here’s an explanation.
The Eclectic Light Company 