A cookie sheet is a flat, rectangular baking pan used primarily for baking cookies. It typically has low sides or no sides at all, allowing for easy access to the cookies and promoting even baking. Cookie sheets are usually made from materials like aluminum or stainless steel, which conduct heat well, ensuring that cookies bake evenly. These sheets can come in various sizes and may have a non-stick coating to prevent cookies from sticking. Some cookie sheets also feature raised edges, which can help contain any melted chocolate or toppings. They are an essential tool in any baker's kitchen, especially for making treats like chocolate chip cookies or sugar cookies.