History
Ancient postal history dates back more than 4,000 years to Egypt, according to Postal Services History at LookD.com. The first postage stamps in the United States were issued July 1, 1847 by the Post Office Department, according to the U.S. Postal Service.
Function
Merriam-Webster dictionary defines postage stamp as "a government adhesive stamp or imprinted stamp for use on mail as evidence of prepayment of postage." Stamps are basically a form of currency traded for the services of delivering pieces of mail or packages. They are affixed to letters and other types of mail before posting.
Types
U.S. postage stamps, including first-class stamps, come in two types: self-sticking and gummed. Self-sticking stamps are like stickers and can be peeled off the backing and adhered to the mail. Gummed stamps must be moistened before they will stick to the paper of an envelope or package.
Size
First-class postage stamps are typically square or rectangular, although some certain commemorative stamps can be other shapes. The typical "forever" stamp sold by USPS is just under 1-inch square and is the typical size for most first-class postage stamps.
Designs
First-class postage stamps come in a variety of designs, including commemorative stamps to honor notable figures in history to those priced above the usual first-class rate with the difference going to a cause, such as breast cancer research.