A sheet pan is a large, flat baking dish typically made out of metal with sides that are between 1/4 to 1 inch high. The name comes from its resemblance to a standard piece of paper or cardboard that you would fold up into thirds (a "sheet") before using it as a pan for cooking food on both sides at once, hence the term “pan”. Sheet pans are commonly used in baking and can be found in various sizes from small 9x13 inches to large 24x24 inches. They're perfect for roasting vegetables or meats, making desserts like cookies or brownies, or even cooking a complete meal with multiple dishes on one tray.