Terminology
The term "philately" means the study of postage stamps, postmarks and related items. A philatelist is an individual who studies or collects these items. Philatelic organizations around the world include the United States Stamp Society and the Cinderella Stamp Club in London, England.
Types of Stamps
Coil stamps are stamps that appear in rolls. Vending machines originally sold these.
Joint-issued stamps are internationally released commemorative stamps that honor a person or event that affected multiple countries. For example, in 1986, both the United States and France released stamps to celebrate the centennial of the Statue of Liberty.
Mint stamps are stamps that remain unused. They are usually more valuable than used stamps.
Airmail stamps are stamps for deliveries transported by airplane. For example, mail that travels overseas would require an airmail stamp. The term "aerophilately" denotes the branch of philately that involves the study of airmail.
Value
The most valuable stamps are those that are rare, in demand and in mint condition. For example, the 1918 Inverted Jenny is a rare and expensive stamp that erroneously features an upside image of an airplane.
The First Stamps
The first stamps in the United States appeared in 1847. They featured Benjamin Franklin and George Washington. Since then, those men's faces have remained common for stamp designs.
Airmail service in the United States started in 1918. Military personnel made the first flight.