This is a French 19th-century term used in an art-historical context to describe a type of subject matter for painting. Such pictures were particularly favoured in the Netherlands in the 17th century and many artists specialised in their production. They showed both peasant life (as in the work of Adriaen Brouwer, Adriaen van Ostade and David Teniers) and bourgeois urban life (as in Ter Borch, Metsu and Vermeer).
Genre subjects, however, were seen as one of the lowest in the hierarchy of paintings established by the French Academy. See the entry for The Genres.