Mission Teams are a new feature whereby you gain team ranks by completing missions while enlisted in a team. Each team has a commander which will deliver missions, commenting on your success or failure. Ranking up be completing missions will earn you rewards like calling cards, emblems, and Rig cosmetics.
Two of the four Mission Teams will be available in the beta. The JTF Wolverines are all about aggressive combat, while the Orion Initiative favors strategy and objective based missions.