To understand it, you'll first need to know that the earth has natural magnetic fields. The magnetic charges from these fields can build up inside your monitor, causing a loss of color accuracy. Degaussing scares the bad magnetism out of the monitor and fills it with good karma. If your monitor doesn't have a degauss button, fear not -- many new monitors automatically degauss themselves. If you have a flat-panel display, there is no degauss button because magnetism doesn't build up in flat screen displays.
You should be able to access the degause reset by finding it on the buttons on the monitor. It might be listed in a bud catagory so look for it. Usually the icon it looks like a upside-down horseshoe with a lighting bolt thru it / or something with 3 circles
It will make your monitor look like this for about 2-4 seconds so dont freak