Quite simply, this addon tracks your hits, crits, and their % of happening so that you know your REAL actual legitimate hit and crit % chance, instead of the theoretical one given to you on the character pane. Also, this'll track how often common [older] enchants go off, to see how often your crusader, lifesteal, fiery [etc] enchant goes off. Note that while duel-wielding, an enchant will do HALF the oftenness since that weapon only accounts for HALF of your hits. This is useful for high-level characters to tweak & adjust their gear to help counterbalance what their weakpoint[s] might be.....and for entertainment.
For commands in-game type /PROCS HELP and it'll give you directions. Normally, this constantly tallies your percentages until you log out.....but you can turn on LIVE mode which'll reset each fight and tell you what that fight had [spams the chatbox with a line every fight, though]