A font server is a net service that provides a set of X11 fonts
with a simple protocol. It can be queried which fonts it provides and
will supply the font bitmap data on request.
You might want to use a font server to provide the X server with a
modified cursor font, instead of telling it where to find the font on
the file system.
This method is especially handy if you use several machines that don't
share a common file system or if you use X terminals that support
the font server protocol.
A font server program and associated tools comes with the X11R5+
distribution (AFAIK).
Setting up a font server
Read the manual pages fs(1), fslsfonts(1) (or
xfs(1), xfslsfonts(1) under X11R6) and try it—it isn't
hard. Say, you are running the server on host some.host.edu
on port 7100. You can test the setup with the command