Postcards are an extremely popular field of philately. A postcard is a rectangular-sized cardboard for correspondence usage. Such cards are pre-typed with appropriate text indicating how to use the card, a limited area for writing the message and a preset fee, usually lower than the fee for mailing out a letter.
While some postcards are uniface (no printing on the other side), others have some specific printing such as touristic locations, ancient and classical monuments, sites of churches, features of towns (central squares, main roads, medieval structures, famous buildings, etc), trains and railway structures, bridges, views of coasts and landscapes, statues, paintings, museum exhibits, scenes of everyday life and much more.
With the invention of photography, in historical terms, postcards have captured and preserved many aspects of human civilisations and achievements. This wealth of information is today essential to the reconstruction of the history of many towns and sites around the world.
In philately, postcard collecting not only allows such historical reconstructions, but also provides useful research as to the postage services and rates used at the time, including the use of postmarks from towns and cities, some of which may not exist today. Depending on the period and location, some ''limited printing'' postcards can be scarce.
Postcards require a postage stamp to be adhered to it before its mailout.
Postal cards have the postage rate detailed on them.
A modern Australian postcard