First used in place of postage envelopes in England during the 1830s, postage stamps serve as proof of postage paid to postal services all over the globe. Although most stamps today are self-adhesive, some stamps, like those used for precanceled mail, are still stamped on the envelope using a machine or a hand stamp, and pre-stamped envelopes and stamps requiring water to activate the adhesive can still be purchased through the U.S. Postal Service. Each country prints its own stamps, but no matter where you are, the types of stamps are the same.
Like the United States "Forever" Liberty Bell stamp, definitive stamps can be used for postage all the time. Typically featuring flags and historic figures, definitive stamps are smaller and simpler than most other types of stamps, using only a few colours. The first definitive stamps in the United States were printed in 1847, and featured George Washington and Benjamin Franklin.
Larger in size and printed in smaller quantities than the definitive stamp, commemorative stamps recognise an important event or an organisation, like the American Cancer Society. They are not reprinted after the original print run sells out. The first commemorative stamp printed in the United States was created to honour Columbus's discovery of the New World. Called the Columbian Exposition issue, the stamp first appeared in 1893.
Stamps to celebrate holidays and other unique stamps, like the "Love" stamp series, are considered to be special stamps by collectors. Like definitive stamps, special stamps are often available for a long time and may be reprinted. However, like commemorative stamps, they're often larger than a definitive stamp.
Although the first-class stamp can be used on almost anything, individual stamps can be purchased through the U.S. Postal Service for postcards, international and priority mailings. Additional postage stamps are also available to purchase through the U.S. Postal Service in a variety of nonstandard denominations.