Teams are used in both Trackers and Analytics for two different reasons.
Teams are not used the Permissions tab to manage content access.

 

In Trackers, Teams are used to save views and to restrict row with the Permissions column.

In Analytics, Teams are used to group users for filtering. They allow role independent reporting. For example, if a company has multiple roles with different levels of content access you can apply a broad company team name to all users in those discrete roles.
Filtering for a Team name in Analytics gives you insight into data room use by the entire company.