There are a variety of reasons why developers use globally unique identifiers (GUIDs), such as assigning unique identifiers to classes or when dealing with databases. This tip contains sample code ...

GUIDs are not really designed to be used as security tokens -- they are unique but not secret. The (pseudo)-random process that generates them is not necessarily cryptographically secure.

Non-random GUIDs UUIDs or GUIDs, whichever you prefer to call them, are a Universally Unique IDentifier, and they get used all over the place.