A team is a collection of Members working on different projects together. When you create a Team, every Team Member has access to any Project within the Team. However, every member does not necessarily have to work on every project.
There are two types of teams, Free Teams, and Premium Teams. There is no limit on the number of Projects within any Team. Free Teams have a limit of 10 members, who have access to every Project the Team is working on. Premium Teams do not have a member limit, and also have access to Private Team Projects, which allow restricted access to certain Team Members.
To see all benefits of upgrading your Project to Premium, click here.