Group Policy Objects
Group Policy is a framework for grouping settings together as a single entity and having them applied to many computers. Group Policy is stored in Active Directory in a central location. After a new Group Policy Object (GPO) is created, it can be linked to different Active Directory containers, OUs, domains and sites. By inking a GPO the computers and users will receive the settings stored in the GPO the next time Group Policy is refreshed on the client computers. The default Group Policy cycle is every 90 minutes plus a random offset of 30 minutes.
It is during the Group Policy refresh that all the settings in the linked Group Policy Objects apply, it is also at that time that the Specops Group Policy based products perform their work on the client computers.
Read more about Group Policy in this document from the Microsoft website.