In your team, you can have 4 different kinds of users: Team admins, creators, collaborators and viewer. To set up your teammates roles, you need to go to Add/remove teammates in the menu. Here, you can see their rights and permissions:
Typical use cases for each role:
Viewer: Somebody who only watches and annotates playtests from colleagues, but who cannot order themselves and also is not able to submit orders for approval
Collaborator: Somebody who is able to submit orders for approval
Creator: Somebody who can order but not manage the team/billing
Team admin: Somebody who can order and manage the team/billing
Further, creators and team admins can approve orders that were submitted by collaborators by default. There is also an option to disable this functionality for each user (although at least one approver must exist in each team).
Please note: The role of collaborators (and the approval functionality) is only available for enterprise and pro-advanced customers.