About this term
Source: Oxford University Press
Art form usually comprising a design of images and lettering printed on paper and generally mass produced for display in public places such as on walls and hoardings. The early development of the form in the 19th century was closely linked to the introduction of lithography, since when its evolution has been bound up with subsequent advances in printmaking techniques. The access to a large public has attracted many artists to the poster and allowed it to be harnessed for a number of social purposes, such as the dissemination of information and propaganda; it has also made it one of the most significant forms of Commercial art.
From Grove Art Online