Linns.com mentions postage stamps as the most recognizable form of stamp. Definitive issues are workhorse stamps, which means they are usually in circulation for longer periods of time. Commemorative stamps honor people, places or events. Special stamps include ones with a special theme such as a holiday.
Linns.com further notes that definitive issues tend to be smaller in size and are released in several formats that include booklets or coils. The 1840 Penny Black stamp of Great Britain was the first stamp issued, and it was a definitive.
Commemorative stamps are larger in size and are in circulation for a limited period of time. There is debate over which commemorative came first in the United States, but the 1893 Columbian set is considered one the earliest forms out there.
Special stamps include not only holiday stamps such as Christmas and Thanksgiving, but other holidays such as Hanukkah and Kwanzaa. Love stamps and greeting stamps are common in this category as well.
There also special-purpose stamps designed to cover certain fees or services. Some stamps in this category are AR fiscal postal, C airmail and B semi-postal. These types of stamps cover charitable donations or certain taxes. Some stamps exempt the assessment of postage, while others label a piece of mail as needing additional postage.
Postal tax stamps are used to collect taxes within a certain period of time. Occupation stamps circulate under the authority of an army or occupational government. Stamps such as these are normally found during a conflict or after peace has been negotiated.