What exactly is GUID? Why and where I should use it?

Question

What exactly is GUID? Why and where I should use it?
I\'ve seen references to GUID in a lot of places, and in wikipedia, but it is not very clear telling you where to

Answer 1

Someone said they are conceptually 128-bit random values, and that is substantially true, but having done a little reading on UUID (GUID usually refers to Microsoft's implementation of UUID), I see that there are several different UUID versions, and most of them are not actually random. So it is possible to generate a UUID for a machine (or something else) and be able to reliably repeat that process to obtain the same UUID down the road, which is important for some applications.