The unique boards made of a teflon like material come in several sizes (Armstrong carries the 5 most popular at the moment) and have the ability to seal after being cut. Both sides can be used for cutting.
One side is plain and the other is segmented into half inch squares. Perhaps the most significant feature of these mats is the added longevity they give to your blades as they do not dull blades like cutting on wood or cardboard surfaces can. And of course, they protect the surface you are cutting on.