The Friends list (previously named invite list) is simply the list of players that you can choose to invite to a new Warzone game. By default, anyone you play a multi-player game with is automatically added to your friends list.
 Adding to your friends list
You can add new players to your friends list by visiting their profile and clicking "Add to friends list". After doing this, they will show up when creating a new Warzone game.
If you're trying to invite a friend to your game, it's often much easier to simply bypass your friends list and invite them via their e-mail address. If you enter the e-mail address of their existing Warzone account, it functions identically to as if you had them on your friends list. If you enter an e-mail address that is not registered with an account, they will be sent an e-mail and can easily create an account.
 Viewing and removing from your friends list
You can view and manage your friends list from the manage friends list page located under the Settings tab.