There is a standard user name called DEFAULT USER and a standard computer name called DEFAULT COMPUTER. When the policy downloader updates machine- and user-specific policies, it first tries to find an entry in the policy file for the local computer name or user name. If the downloader does not find an entry, it looks for the DEFAULT USER or DEFAULT COMPUTER entry and uses those entries for the update. If there are no entries for a particular user or computer and default entries do not exist, no update takes place.
The DEFAULT USER and DEFAULT COMPUTER entries are powerful because administrators can set policies for a large number of users and computers and then manage the exceptions by creating specific user and computer entries in a .POL file.