The directory containing the never-changing game files, such as programs, help files, and the standard ship list and starchart. In one sense, this is the root of your VGA Planets directory tree.
Player Side: The directory which contains your client program. Usually, your game directories are sub-directories of the root directory.
Host Side: The directory which contains the hosting programs. The game directories often are sub-directories of this one.
Normally, you cd into the root directory (or, configure the working directory accordingly under Windows), and start the programs you wish. PHost also allows you to specify the root directory name on the command line if it differs from the current directory. Some programs can also find the root directory on their own.
See also: Game Directory, Hosting with PHost.