Street art

Street art is visual art created in public locations, usually unsanctioned artwork executed outside of the context of traditional art venues. The term gained popularity during the graffiti art boom of the early 1980s and continues to be applied to subsequent incarnations. Stencil graffiti, wheatpasted poster art or sticker art, and street installation or sculpture are common forms of modern street art. Video projection, yarn bombing and Lock On sculpture became popularized at the turn of the 21st century.

http://en.wikipedia.org/wiki/Street_art