Group Policy is applied to a user or computer.

Based upon where the user or computer object is located in the Active Directory. The computer’s GPOs are applied at computer startup. The user’s GPOs are applied at login. However, in some cases, users may need policy applied to them, based upon the location of the computer object, not the location of the user object. The Group Policy loopback feature gives the administrator the ability to apply Group Policy, based upon the computer that the user is logging onto. The computer’s GPOs are still retrieved at computer startup, but the user portion of these GPOs isn’t applied until a user logins in