Think of learning to use the Force like your own experience then. Some can do it, some can't. Those that do, hopefully learn to control it without letting it or anyone control them.
They are just some of the factions, but probably the most well known over history. Jedi focus on the Light Side of the Force and the Sith focused on the Dark Side. Neither of which are inherently evil in my opinion, though some will tell you otherwise. As with anything else, there are always those that abuse their power and teachings for their own agendas.