Teams can be used to determine visibility of Apps and also for Read-Only and Full access rights to records.
When setting up users and teams, first consider which groups of users will be using the site. For each group of users determine which Apps they should have available and which records in those Apps they should have access to. Then create teams for these groups of users.
Creating a Team
Click on the launchpad in the top left and then the COG to access the Settings area.
Select the 'Team Settings' App and in the left pane menu click on '+ New Record' below 'Team Settings' and it will bring up the property sheet that you can define your new team in.
The team 'ID' will be populated automatically. Select an appropriate team Name, once this Field has data in it the Team will be created.
Note: When you create your first Team it will populate this Team with all the current users on the site.