What do you think what is graphics tablet?
Our electronic definitions web site has answer for that as well:
is a device used to input line drawings directly to a computer. The user `draws`
with a `pen` onto a flat pad possibly copying a diagram or drawing freehand. Tablets detect the position and movement of the `pen` in a variety of ways (e.g. a matrix of wires embedded in the surface the angular movement of a supporting arm). Also known as a graphics pad.