This game specifically will give you a steam key you redeem in the steam client. Not all games are like that (some are origin, uplay, or you download directly from amazon.) Anytime you're curious about whether its steam or not you should be able to hit ctrl f and type in steam. If it brings it up saying it requires the steam client you'll get a key, if not its probably going to be one of the other options. You can still put it in your steam library as a non-steam game even if its not a steam key so your friends can still see what you're playing and you still have access to ingame chat, but it wouldn't have any steam specific features (achievements, cloud saving, etc)