The optical mouse processes information about its movement without the need for the little ball on the bottom common to earlier mouse's (mice?). There's no mechanical device to get dirty, wear or come apart, since the movement is detected by light sensors. Additionally, it doesn't require anykind of mouse pad since it can be used equally as well on smooth surfaces. It does suffer some limitations on the color of surface on which it's being used, however. Mine doesn't particuarly like light colored ones and absolutely detests white ones. Other than that, the erratic behaviour of the pointer when the mouse's receiver is to close to the computer or other electrical device as well as the same phenomena when the batteries in the mouse begin to lose their charge. Otherwise, I highly recommend them (mine is manufactured by Logitech).