A stamp is a small piece of paper, often rectangular, that is used to indicate payment for postal services. It typically features a design, such as an image or text, and is affixed to an envelope or package before mailing. Stamps come in various denominations and can be collected as a hobby, known as philately. Stamps are issued by national postal authorities and can represent significant cultural, historical, or artistic themes. They serve as a means of validating postage and can also be used for other purposes, such as tax stamps or revenue stamps in different contexts.