Key art, also known as key visual, is the artwork which is repeated across media such as posters, print, television and digital advertisements, streaming or download thumbnails, and game or film DVD/Blu-Ray box covers.
Key visuals are defined in the field of media studies as "functional equivalents to keywords" that "emerge, or... are strategically produced and distributed... and considered worth being archived, remembered, called for and used as a major element in (audio-) visual horizons of actions and means of co-ordination or (ex-)communication for some time."[1]
Key art is most commonly understood as advertising for entertainment media such as films, television and video games.[2][3]