Ceramic tile can easily be made into a variety of sizes and specifications because it is formed by a human process. It begins as clay (usually comprised of shale, gypsum, and sand) and is forged into a material known as bisque. Bisque is then shaped into tiles and fired, usually in a kiln. Typically, the higher the temperature the tile is fired in, the stronger the tile will be. Ceramics can be glazed, unglazed, basic, or decorated and are used in a variety of applications, though most commonly for walls and floors. Being naturally porous, most ceramics are typically glazed (either before or after being fired).
The Porcelain Enamel Institute (PEI) has a ceramic tile rating system that gauges abrasion levels and rates tiles for wear-resistance of a scale of 5 categories: Class 1 – 5+, with Class 1 being rated for “no foot traffic” recommended and Class 5+ being suitable for “extra heavy traffic.” (For example, an entryway should have a tile that’s rated for high foot traffic, is easy to clean, and resists moisture).