A pastry bag is a kitchen tool used for decorating and filling pastries, cakes, and other desserts. It is typically made of flexible material, such as plastic or cloth, and has a pointed end where various tips can be attached. This allows for precise control when piping out frosting, cream, or dough in different shapes and designs. To use a pastry bag, the user fills it with the desired mixture and squeezes from the top to push the contents out through the tip. This technique is essential for creating decorative elements like rosettes, borders, and intricate designs on baked goods, enhancing their visual appeal.