yeah pretty much what Psychotic said.

XIII is pretty straightforward but then there was all this hullabaloo about how bad it sucked (which it does), so SE decided to make XIII-2 and screwed it all up and made it worse. The only upside to the modern era FF is that it's more "new player friendly" - less confusing with tons of side quests and having to go out of your way to get summons (XII is the last one where you have to actively hunt them down if you want them.. I'm hoping XV will be different, though) ..

But anywho... Welcome!