From the Wotc Website:
Illustrated cardstock terrain tiles for use with the Dungeons & Dragons Roleplaying Game.
This product adds a new dimension to D&D games and gives Dungeon Masters an easy and inexpensive way to include great-looking terrain in their games. This set provides ready-to-use, configurable tiles with which to build exciting dungeons, temples, and monster lairs. This accessory for the D&D game contains six double-sided sheets of illustrated, die-cut terrain tiles printed on heavy cardstock.
From the back of the product:
This pack contains six durable, double-sided, fully illustrated map grids, featuring forests, ruins, and other terrain elements that you can use to make great D&D encounters that enhance your roleplaying game experience.