A project team usually belong to different groups, functions and are assigned to activities for the same project. In order to use the approval chains and work types, you will need to add a team and assign the users.
The assigned team members are responsible in making sure that all final work to follow through the approval chain process as directed and assigned by you (Team Leader).
The other usage of Teams can be used in messaging, where you can send a group message to a specific team instantly.
To know more about how to add your team members, READ HERE.