What do you mean by 'what they are'? I'm afraid I can only really help as much as digging through what I assume to be relevant bits of core codebase and scanning for the word Delegate then seeing what I guess it does...which i suppose you can manage if you're tackling this extension :)
If in doubt stare at pages of code until something useful pops out... (i dont necessarily recommend that technique..i've lost days of my life to it :|)