HR84

We use the HR84.4-.8 for PF, and I have never touched the others. Here is what I found from HR Tech Text:
Use Position Reason Code (HR84.1) to define a position reason code. A position reason code represents a reason for a change to a position code, such as corporate reorganization, new supervisor, salary change, and so on. Choose the Mass Entry button to define many position reason codes at once. Assign position reason codes in PA02.1 (Position). Press Define in the Reason field to access this window.
Use Budget Reason Code (HR84.2) to define BD (Budget Reason) type HR codes, for example, new position, growth, restructuring, and so on. Assign budget reason type HR codes in PA70.1 (Position Budget) and PA71.1 (Job Budget). Press Define in the Reason field to access this window.
Use Requisition Cost (HR84.3) to define AR (Applicant Rating) type HR codes, for example, good, interested, excellent, not qualified, and so on. Assign applicant rating codes to applicants in PA31.1 (Applicant). Press Define from the Rating field to access this window.
Use Incident Status (HR84.9) to define IS (Incident Status) type HR codes.

I hope this helps!