Running GUI programs remotely

It used to be that you would set the DISPLAY variable
and use xhost to run GUI programs on remote machine
and send traffic to your desktop. It seems the modern
way is to use ssh tunneling for X11 traffic.

This is accomplished by simply running:

ssh -fY host program

E.g.:

ssh -fY user@hostname xclock

Internally ssh establishes a connection to remote machine,
starts a proxy server listening to port (e.g. 6010),
sets the display variable (e.g. DISPLAY=localhost:10.0),
and starts the requested program (e.g. xclock).
xclock sends all X11 traffic to the server spawned
by the ssh process, and forwards it to your desktop's X server.