A mouse pad is a flat cloth or plastic object that is commonly rectangular and gives an optical-mechanical mouse more traction and an optical mouse an easier-to-read surface. In most situations, using a mouse pad can make moving the mouse cursor easier and more fluid. The image below shows a SteelSeries cloth mouse pad.
What is a mouse mat?
Alternatively known as a gaming mouse pad or desk pad, a mouse mat is a much larger version of a mouse pad that accommodates the keyboard, mouse, and other accessories. Mouse mats are popular with gamers because of their larger surface, non-slip bases, and are usually higher quality. There are even mouse mats available with RGB edges.
Should I use "mouse pad" or "mousepad" in my writing?
Both "mouse pad" and "mousepad" are correct and are both widely used. The version you use depends on the style guide you follow. Computer Hope has chosen to have a space between "mouse" and "pad" in all its writing.