GUID

A globally unique identifier or GUID is a unique reference number used as an identifier in computer software. The term GUID also is used for Microsoft's implementation of the Universally Unique Identifier (UUID) standard.

The intent of UUIDs is to enable distributed systems to uniquely identify information without significant central coordination. Thus, anyone can create a UUID and use it to identify something with reasonable confidence that the identifier will never be unintentionally used by anyone for anything else. Information labeled with UUIDs can therefore be later combined into a single database without needing to resolve name conflicts.