Group Policy is a built-in feature of the Microsoft Windows operating systems. Group Policy allows administrators to automatically configure myriad options within the OS. These policies can be configured, and applied, either locally to the computer via Local Group Policy or remotely within an Active Directory environment.
Microsoft has added Group Policy Preferences Client Side Extensions, formerly a third-party tool called PolicyMaker, to its in-support Windows OSes. The CSEs greatly extend the number features which can be configured via Group Policy.
See the following links for more details.
http://gpsearch.azurewebsites.net - Searchable list of configurable group policies http://blogs.technet.com/grouppolicy - Microsoft’s official Group Policy blog http://blogs.technet.com/askds - Ask Directory Services is the official blog from Microsoft engineers supporting group policy and other related AD technologies