Team behaviour changed in February 2018. If you used Plecto before this date, please check our help article called "Legacy team behaviour"
Teams are a way to enforce permissions and limit widgets to display data for only specific employees.
If your widget does not have a team filter, then all employees, even the ones not assigned to a team, will be displayed. This makes it much easier to get started with Plecto, since you don't need to know about teams at all to get some data on your dashboard.
Limit access: You can limit access to dashboards, if you don't want teams to access each other's numbers. Read more here.