Graffiti originated in ancient Italy as inscriptions and drawings on sculptures and walls. In fact, graffiti was found in 1851 in the ruins of Pompeii. Painting on sidewalks, and other forms of graffiti, is still common in Rome today. Whereas Romans consider graffiti as a form of urban art, many westerners consider it vandalism unless property owners give consent to the graffiti artists. Graffiti may include drawing, painting, and writing, or a combination of the three.

Tagging is a form of graffiti used to put a 'name tag' on public areas and is thought to be used by some gangs to mark territory. The origin of tagging goes back to the 1970s when a mail carrier in New York made a goal to ride every bus and subway in New York. He wrote his name and courier identification number, Vic 156, to mark each bus and subway he took. Others began to follow Vic's example and tags grew more prevalent, larger, and much more elaborate. Tagging as graffiti moved from buses and subways to walls and all types of outdoor areas.

The old Belmont trolley tunnel in Los Angeles was a popular spot for taggers until, despite over 2 years of protests to save it as a modern cultural landmark, the graffiti covered tunnel was torn down. The tunnel was frequented by homeless people, gangs, and drug addicts and had appeared in many films. Graffiti artists and taggers from other states and other parts of the world had traveled to paint at Belmont. Los Angeles police dismissed the graffiti as tagging by vandals, but art groups appealed to the Los Angeles Cultural Heritage Commission to help save the tunnel.

"Aerosol muralists" are graffiti artists who paint large, commissioned murals on urban walls, usually on the sides of businesses. The murals can be very beautiful and graphic, attracting much attention from potential customers in the area. Aerosol muralists use aerosol spray paint as it gives an airbrushed look to the mural. Sometimes house paint, rollers, and brushes are also used. The murals usually relate to their surroundings. For example, a mural on the side wall of a Greek restaurant would most likely have a Grecian theme.