Postcard collecting is a popular hobby with a history that reaches back to the late 1800s. The first postcards entered the market in the late Victorian era as rewards for schoolchildren or promotional materials. The Smithsonian Institute published a short article on this history of postcards, which you can read on their website. Due to the wide range of styles and subjects, collectors tend to focus on one or two types, such as mailed postcards from the Edwardian era.