In team mode, multiple players and mobile devices can be joined to the same team. Once a participant from a team completes a mission, that mission shows as completed for the whole team. Points will be tallied for the team as whole, and displayed with the team name and team photo on the Leaderboard.
To add teams to your game, head over to the Participants tab in the game manager and set the Game Mode to "Teams"
You'll have the option to either pre-create teams in advance or to allow participants to create their own teams.
Full details on managing teams and participants in your game can be found here.