In the case of Call of Duty: WWII those rewards include cosmetic perks like different skins for guns, social emotes, soldier apparel, and multiplayer call signs.
You should be able to just sign - in on your Xbox 360 console and play any online multiplayer game (i.e. Halo, Call of Duty, Battlefield, or whatever) and access to apps such as Netflix (provided that you have a subscription).