PROCESSENTRY32.pcPriClassBase, GetPriorityClass, GetThreadPriority: Meaning/Relation?

Can someone please define PROCESSENTRY32.pcPriClassBase, GetPriorityClass, GetThreadPriority and possible answer:
[list=1][*]What are some constants to define the values given by PROCESSENTRY32.pcPriClassBase, if any.[*]What is the relationship between GetThreadPriority and GetPriorityClass? They both seem to be giving the same information, GetThreadPriority more descriptive than GetPriorityClass; however I honestly don't know.[*]Does PROCESSENTRY32.pcPriClassBase give the same information as GetThreadPriority or GetPriorityClass?[/list=1]

Come on... somebody?