The full form of UUID is Universally unique identifier.

Universally unique identifier is a universally unique identifier is a 128-bit number used to identify information in computer systems. The term globally unique identifier is also used, typically in software created by Microsoft. When generated according to the standard methods, UUIDs are, for practical purposes, unique.

UUID defined in rfc4122 as below.

   This specification defines a Uniform Resource Name namespace for
   UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally
   Unique IDentifier).  A UUID is 128 bits long, and can guarantee
   uniqueness across space and time.  UUIDs were originally used in the
   Apollo Network Computing System and later in the Open Software
   Foundation's (OSF) Distributed Computing Environment (DCE), and then
   in Microsoft Windows platforms.

   This specification is derived from the DCE specification with the
   kind permission of the OSF (now known as The Open Group).
   Information from earlier versions of the DCE specification have been
   incorporated into this document.