A User's role may change within their Organisation. This may mean that their Team membership needs to change in order for them to have more or less access to particular Apps and Records.
To remove a user from 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 then click on the Team from the list that you want to remove the users from. This will show you the current Users that are in the selected Team.
From here click the 'x' next to the User to remove them, this is a choice you will be required to confirm and once confirmed the User is removed from the Team.
Note: If there are Teams on a site then a User needs to be a member of at least one Team. If this Team is the only Team that a User is a member of, they must be assigned to a new Team before they can be removed from this one.