Stamp collecting is generally accepted as one of the areas that make up the wider subject of philately, which is the study of stamps. A philatelist may, but does not have to, collect stamps. It is not uncommon for the term philatelist, correctly or incorrectly, to be used to mean a stamp collector. Many casual stamp collectors accumulate stamps for sheer enjoyment and relaxation without worrying about the tiny details. The creation of a large or comprehensive collection, however, generally requires some philatelic knowledge and will usually contain areas of philatelic studies. Postage stamps are often collected for their historical value and geographical aspects and also for the many different subjects depicted on them, ranging from ships, horses, and birds to kings, queens and presidents. Stamp collectors are an important source of income for some countries who create limited runs of elaborate stamps designed mainly to be bought by stamp collectors. The stamps produced by these countries may exceed their postal needs, but may also feature attractive topical designs that many collectors desire.