This page provides the following information
What is GUID
GUID : Global Unique Identifier. It is used to identify an object and to ensure its unicity. The object GUID's are generated during the analysis and are saved in the Knowledge base.
If between two versions of analysis, the GUID of an object has changed, the analyzer sees it as a new object and it creates a new object.
The analyzers for which the GUID is calculated are :
How to find the GUID of an object
You can find the GUID of an object by following the below page once you know the object name.
GUID Format per technology
For a given technology, the GUID formalism is the same for all type of objects.