There are a number of victory types in the game. There are actually five official ones. Science is one that is fairly easy to win. It is fun for those who love science like I do but may be more difficult for others. Most find it is a favorite type. Then there is Culture which can be tricky but is also a lot of fun if you are up for the challenge.
Domination is yet another and Religion which I love because it can be very thought-provoking and very controversial. Then, Score is a great one too and you might add in Diplomacy and Gathering Storm if you'd like to. To win at this game, you have to reach one of the victories except for Score. And, you have to do so before any other player does. This is a lot of fun but certainly can be hard to accomplish.