clsid:A977FF0C-8757-4E76-8533-482F91946233
Apparently that's an example. So is {000209FF-0000-0000-C000-000000000046}.
Why does this matter? Well, as generally with the Wiki, selection of the title provides "backreferences".
CLSID stands for Class Identifier. This sort of UUID is used in Microsoft's COM code to identify classes. Normally you would use the ProgID which is a more human readable equivalent when creating instances of COM classes.
Notice Chin Huang's provision of a brief script to list ProgID for the applications a specific host knows, on the registry page.