Alright so uh steam it's got your library of games, it has a store where you can buy digital copies of your games. It has a community section to look at guides, talk in groups, etc. You have a friends list you can chat to those friends.
Uh you can get game achievements too, provided said game has it. I <3 that bit. Though I'm sad ff13 doesn't have many achievements.
Steam also has a site
http://store.steampowered.com/
Er there are adult games on there too btw. But there are family friendly games too. You do get asked about age for the adult ones.
Origin is kind of the same as steam but tbh not as huge.. or community based.
https://www.origin.com/aus/en-us/
Origin is where I go play sims from.
I have both installed on my pc, cause then you use that to open the games installed to each.
That help? otherwise the sites should.
Yes I have X and X-2 then 13, 13-2, 13 lightning returns.