They were first started to be an order of priests that was better educated than typical priests in order to fight against protestant attacks on the Church and they were closely connected to the Pope. They did a lot of good things during the counter reformation, played a key role in missionary efforts in Latin America, North America, Asia, and Africa, and established schools all over the world, among other things. But after Vatican 2 they went downhill fast. There are some jesuits I've known who are great people, but there are also many that are literal marxists. The jesuit magazine "America" is absolute filth. And they think that because they're so educated they're right about everything. Some want the Church to become a moral relativist, liberal christian church with gay marriages, women priests, premarital sex, abortion, and everything else evil. They have the least amount of fidelity to the magisterium of the Church of all the orders of priests.