Teams is a concept that is often used by large domain holders or MSP's. This allows you to group domains and users into groups and provide fine grained access to each of these users. 

A typical use case would be to create a team for a customer, add their domain to the team and then invite the customer to the team. 

They will login to your portal and only see the reports you have specified in the team settings. 

Customers can belong to multiple teams. 

Adding Members