Wacom is simply the manufacturer of a tablet and generally considered as the best on the market. They have a couple of versions from the smaller "Bamboo" tablets to larger Intuos range (that can be bought A5/A4/A3 size), all of which are tablets that you draw onto using the tablets pen.

When you draw on a graphics tablet the position of your pen on the tablet corresponds to the position of your mouse cursor on your monitor. So if you have previously drawn with a mouse, its absolutely no different, presumably you don't look at your mouse/desk while you are drawing

Wacom also do the "Cintiq" range which is essentially a monitor/screen that you draw directly onto, so you can see yourself drawing on the image, however these will set you back a couple of thousand.