The xscreensaver program waits until the keyboard and mouse have been idle
for a period, and then runs a graphics demo chosen at random.  It turns off
as soon as there is any mouse or keyboard activity.

The purpose of xscreensaver is to display pretty pictures on your screen
when it is not in use, in keeping with the philosophy that unattended
monitors should always be doing something interesting, just like they do
in the movies.

However, xscreensaver can also be used as a screen locker, to prevent
others from using your terminal while your are away.

Homepage:
https://www.jwz.org/xscreensaver/
