Unless you live under a rock you’ve seen graffiti in some place or other. Even in remote northeastern Montana, I see graffiti frequently; often on the side of a cargo train, sometimes tucked in a corner against an old building, or as a vivid splash of color adorning a faded barn-wood building.
Of course in urban locations the presence of graffiti is much more prevalent. The desire to make a mark on the surfaces we are surrounded by is innate, an urge apparent in mankind’s art expression for thousands of years. Caves of Lascaux ring a bell? Some great photos of this Paleolithic Cave Art (15000 BC) can be found at: http://life.time.com/culture/lascaux-early-color-photos-of-the-famous-cave-paintings-france-1947/#1
The contemporary variation of this time honored expression- graffiti- has existed on the periphery of socially acceptable modes of art-making for decades. However, in recent years graffiti artists’ work has gained appreciation and momentum as both style and materials have evolved, and increasingly it no longer viewed as a sub-cultural movement. A basic overview of the recent history of American Graffiti can be found here: http://www.pbs.org/newshour/art/the-history-of-american-graffiti-from-subway-car-to-gallery/
The evolution of expression begs the question, is there a difference between graffiti and street art? Are they the same thing? According to Graffiti Action Hero, they have nothing in common: http://www.graffitiactionhero.org/graffiti-tag-vs-street-art.html
I find the debate over the variation of expression intriguing. In particular because of the essential purpose informing this mode of expression. Street artists and graffiti artists alike make marks on surfaces adorning the landscape because of the desire to communicate with an audience. In some cases the audience is more specific, as with tagging or graffiti styles that are only recognized among specific gangs- which may be an essential difference in the expression of “graffiti” vs “street art”. Street artists, it should be pointed out, may desire to communicate with several audiences overall; and perhaps with a particular audience- but the lexicon is not as explicitly focused. However, when you make a mark in a location where it will be seen, you are communicating with anyone who has eyes to see it. The weight of the message might have more meaning for specific groups or people, but the essential fact is that it is within view and even those who cannot understand the message understand the intent to communicate.
In that sense, I think that the two are synonymous, and interchangeable. This is most effectively demonstrated by the artist Banksy, whose true identity is in itself an unknown. You can find quite a bit with the bare minimum of digging on this profound work, but a good place to start is the artists’ website: http://banksy.co.uk/ And, to view a selection of this incredibly clever art check out this post on Street Art Utopia: http://www.streetartutopia.com/?p=14015