The Paper Tablet works as an absolute positioning device. This means that fixed coordinates on your notepad map to fixed coordinates on your computer screen.
Computer mice are pointing devices that use relative positioning. Mice indicate their position in relation to their previous positions. For example, if you drag your mouse, the cursor moves relative to where it started. If you then pick up your mouse, and place it somewhere else on your mouse pad the cursor does not move. You need to drag the mouse to a new relative position to move the cursor.