Documentation of Registry functions is where?

Hello -
I'm looking for some documentation of the functions "RegRead" & "RegWrite"
I found the functions in the example "register" channel but haven't been able to find documentation explaining the nature of the passed values. Am I missing something? Can someone explain what's what here:
RegWrite("RegToken", token, "Authentication")

I assume token is the variable value that was passed into: Sub saveRegistrationToken(token As String)
RegToken is ?
Authentication is ?

tyvmia