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

As addition to all the other answers, here is an online GUID generator:

http://www.guidgenerator.com/

What is a GUID?

GUID (or UUID) is an acronym for 'Globally Unique Identifier' (or 'Universally Unique Identifier'). It is a 128-bit integer number used to identify resources. The term GUID is generally used by developers working with Microsoft technologies, while UUID is used everywhere else.

How unique is a GUID?

128-bits is big enough and the generation algorithm is unique enough that if 1,0000,000,000 GUIDs per second were generated for 1 year the probability of a duplicate would be only 50%. Or if every human on Earth generated 600,000,000 GUIDs there would only be a 50% probability of a duplicate.

How are GUIDs used?

GUIDs are used in software development as database keys, component identifiers, or just about anywhere else a truly unique identifier is required. GUIDs are also used to identify all interfaces and objects in COM programming.