Ceramic Tile is a clay tile with a hard glazed surface. It is commonly used on floors and walls of restrooms. Wall tiles are frequently glazed (high gloss) and generally installed on a special tile backer substrate with an adhesive such as mastic. Floor tiles generally have a matte finish (not glazed) and are installed on concrete or a tile backer substrate with mortar designed for floor tile installation. Grout is used between tiles to create a semi-smooth surface and accent the tiles. Grout is porous and should be sealed (after 30 days) to prevent dirt, soil and bacteria from accumulating between each tile. Grout can be difficult to keep clean.