A piping bag is a kitchen tool used for decorating cakes, pastries, and other baked goods. It is typically made of flexible material, such as plastic or cloth, and has a pointed end where various types of nozzles can be attached. This allows for precise control when applying frosting, cream, or other mixtures. To use a piping bag, the desired filling is placed inside, and the bag is squeezed to push the contents out through the nozzle. This technique is commonly used in conjunction with cake decorating and pastry making to create intricate designs and patterns.