It is split into two distinct types of policies. The first contains items such as password policies, whether you can access the control panel and change settings, etc. The second is Group Policy Preference Extensions or GPPE which is often thought of as the "last mile" allowing customization of desktop shortcuts, drive mappings, registry keys, etc.
The object of Group Policy is to allow you to create a consistent, secure, manageable, and customizable end user experience and do as much as possible without having to walk to each workstation..You can watch the recording by clicking on this link: Microsoft Group Policy Presentation.
We'll walk through some of the basics like how to access it, how to see what the polices do as well as how to model what policies are and are not doing to a specific user on a specific computer and some common features and best practices.