Okay, screensavers don't really do much screen saving these days. The idea, once upon a time, was to protect screens from phosphor burn-in. Old-style monochrome screens were particularly bad for this. In time, the letters from your menus (we were using text in those days) would burn in to the phosphor screen. Even when you turned off the monitor, you could still see the ghostly outline of your most popular application burned into the screen itself. As we moved to color screens and graphics, that changed somewhat but the problem continued to exist for some time, partly due to the static nature of the applications we were using.
Time passes, and some bright light somewhere got the idea that if you constantly changed the image on the screen, that type of burn-in would not be as likely. What better way to achieve this than to have some kind of clever animation kick in when the user walked away from the screen for a few minutes (or hours). Heck, it might even be fun to watch. The screensaver was born. Modern screens use scanning techniques that all but banished burn-in, but screensavers did not go away. Those addictive fish, toasters, penguins, snow, spaceships, etc., etc. have managed to keep us entertained, despite the march of technology. Let's face it, we are all hooked.
Depending on your distribution, your screensaver may or may not already be active by default. Getting to your screensaver setup involves the same first steps as changing your background. Right-click on a clear part of the desktop and choose Configure Desktop. The desktop configuration card will appear ("You can customize the desktop here"). On the left side of that card, there's an item called Screensaver. Click away.
Like the wallpaper manager before this, you get a nice little preview window over to the right that will give you an idea of what your screensaver will look like (Figure 6-2). The first thing you will want to do is click the "Enable screensaver" check box, assuming, of course, that it isn't already on (the message on KDE 3.1 says "Start screen saver automatically"). Now pick a screensaver from the list and watch the results on the preview screen. To see the real thing in action, click the Test button. To go back to the configuration screen, press any key. Some screensavers can be modified, which is why you also have a Setup button. For instance, the Rock screensaver, which simulates flying through space, lets you change the number of rocks (or asteroids) flying toward you and whether your spaceship moves or rotates through the mess.
Before you click OK, you may want to change the default time before your screensaver kicks in. Mine is set for five minutes. In an office environment (or a busy household), you will probably want to password-protect your screen when you walk away. To do this, click on Require password. When the screensaver starts, you will need to enter your login password to get back to your work. Always remember that your password is case-sensitive.