clubs are atm on the preview, I compare it to guilds on mmorpgs, where you can join like-minded ppl with same interests, like there can be a club for 35+ Forza players from Sweden. You can share posts and you can chat. And then you can use the LFG (Looking For Group) function that are also available. And with that you can make game sessions. Me personally are member of 3 clubs atm, Xbox Preview Club (the official club for preview members), Assassin's Creed club and the one I made for GTN. Clubs and LFG will soon go live for rest of the community.
You can join a club in a few ways,
1: you can find clubs under specific games hubs
2: you can search for clubs under community tab
3: you can be invited to a club from friends and friends friends.
Cogito Ergo Sum | Member of the Month Oct 2016 MyTumblr page