A bread pan, or a loaf pan, is a deep, (usually) rectangular cooking vessel used to shape bread while baking. Dough or batter is placed or poured evenly into the pan. As the bread bakes, it expands against the sides of the pan and the top will rise, giving the finished bread its loaf shape.
Modern bread pans are often made of metal and coated with a nonstick material. Pans come in a variety of sizes and designs.