From the publisher's website:
A basic set of illustrated terrain tiles for use with the D&D Roleplaying Game.
This D&D Roleplaying Game accessory gives Dungeon Masters all of the basic dungeon tiles they need to create great-looking terrain in their games. This set provides ready-to-use, configurable tiles with which to build exciting encounter locations.
This accessory contains 10 double-sided sheets of illustrated, die-cut terrain tiles printed on heavy cardstock, allowing you to create dungeon rooms, corridors, and outdoor locales. The product box is designed for tile storage and as a terrain element in the game.