Guess I forgot to answer the questions.
Bots are programs that play for sites or you. Sites use them to make the tables seem full and more users on the site than there really is. People use them in hopes of making money and not even playing a hand.
There are people who advertise programs that you overlay on the poker site
window and it will show you all the players hole cards. I have never heard of any that work otherwise who would play online.
These two are considered cheating, obviously, and you would get kicked off the site if ever caught with either.
Stat trackers can keep all the stats you could ever want to know about yourself and your opponents. How often they raise, fold, check/raise, call/check, win at showdown etc. and keep all this for you. Some will even try to give you advice on how to play. I don't think they are cheating but I have played enough that I don't think I need them.
You can get a free odds calculator or some for very cheap.