The term "urban" means "from the city" which is derived from the Latin word urbanus. It is associated with art that is created by artist living, depicting, or experiencing city life. The subject is often people living city life and also city buildings and transportation. Urban Art in its rawest form is graffiti. The term graffiti comes from the Italian word graffio which means "to scratch". Graffiti is associated with gang related tagging of territory and a means of gaining attention but it is also associated with humans need to express themselves. Some of the earliest forms of graffiti are the tribal inscriptions of early man on stone hence, the definition "to scratch". One of my favorite pieces of Urban Artwork is a piece that was done by the African American artist, Ernie Barnes.
The piece is entitled "Sugar Shack", a painting that can be seen in the 70's show "Good Times". It's not just the beauty and soul of urban life that makes Ernie's painting come alive, it's the Neo-Maneristic style of the art. You can see the people moving in your mind, although the painting is still. The exaggerated poise of the people show emotion and passion. I do not have the artist's permission to post this exquisite work here (maybe one day I will be blessed to) so it would be a visual treat for you to Google - Ernie Barnes "Sugar Shack".
Another notable Urban Artist is Justin Bua know simply as "Bua". The son of a single mother who was an artist, he grew up with art. He was a latch key kid. As his mother hustled her art on the streets, doing art was his babysitter. He was a break dancer and popper and attributes his style of painting to the rhythm of city people. Justin is noted for being the first artist to chronicle hip hop culture in his artwork. The people who are the subjects of his paintings are totally alive on the canvas and exude the strength and creativity of inner city people. You can read more about Justin Bua and his art at http://justinbua.com/newSite/book.php
One cannot escape the beauty and soul of the city after looking at good Urban Artwork.
Some books of interest:
Street World: Urban Culture and Art from Five Continents
by Roger Gastman, Caleb Neelon, and Anthony Smyrski
Graffiti World: Street Art from Five Continents
by Nicholas Ganz
Urban Illustration Berlin: Street Art Cityguide
by Benjamin Wolbergs
Sources: Wikipedia, Encyclopedia Britannica, Amazon.com, www.justinbua.com, www.erniebarnes.com