Graffiti originally was the term used for inscriptions, figure drawings, etc., found on the walls of ancient sepulchers or ruins, as in the Catacombs, or at Pompeii. But has evolved to include any decorations inscribed on rocks or walls that are considered to be vandalism. However, some people consider graffiti, or some graffiti, an art form; this is usually denoted as urban Aerosol Art.
The practices of graffiti and of considering graffiti as art are generally related to a sub-culture that rebels against extant societal authorities, or against authority as such.
Graffiti art is considered one of the four elements of Hip Hop. Graffiti tagging existed in Philadelphia in the 1960's, pioneered by Cornbread and Cool Earl. Another Philadelphia product, Top Cat, later exported the characteristic Philly style of script (tall, slender lettering with platforms at the bottom) to NYC where it gained populariy as "Broadway Elegant". It wasn't until it reached popularity in the New York City subway system that it took on an extravagant artistic role, expanding from tags to full-blown "pieces". One of the originators of New York graffiti was TAKI 183; a foot messenger who would tag his nickname around New York streets that he daily frequented en route. A Greek-American, Taki was his nickname, diminutive for Demetrius, he took the 183 from his address. After being showcased in the NY Times, the "tag" (stylized signature) was being mimicked by hundreds of urban youth within months. It should be noted that there were other writers active in NYC before Taki, but he brought the most attention to the movement. With the innovation of art, and the craving to gain the widest audience, attempts by taggers were made. What developed was a strict adherence to spraypaint, sampling foreign calligraphy, and the much anticipated mural (that usually covered an entire subway car). The artist was born, called a "writer," and so were groups of associated artists, called "crews". The movement spread to the streets, returned to the railroads where tagging was popularized by Hobos, spread nationwide with the aid of media and Rap music; thus, being yet mimicked again worldwide.
Because they share similar spaces and media, graffiti art is often confused with gang graffiti. There are differences in both form and intent. The purpose of graffiti art is self-expression and creativity, and may involve highly stylized letter forms drawn with markers, or cryptic and colorful spray paint murals on walls, buildings, and even freight trains. Graffiti artists strive to improve their art, which is constantly changing and progressing. The purpose of gang graffiti, on the other hand, is to mark territorial boundaries, and is therefore limited to a gang's neighborhood; it does not presuppose artistic intent.
Graffiti is subject to different societal pressures from popularly-recognized art forms, since graffiti appears on walls, freeways, buildings, trains or any accessible surfaces that are not owned by, or under the control of the person who applies the graffiti. So graffiti incorporates elements rarely seen elsewhere. Spray paint and broad permanent markers are commonly used, and the organizational structure of the art is sometimes influenced by the need to apply the art quickly before it is noticed by authorities. In an effort to reduce vandalism, many cities have designated walls or areas exclusively for use by graffiti artists. This discourages petty vandalism yet encourages artists to take their time and produce great art, without worry of being caught or arrested.
In the early 1980s, the combination of a booming art market and a renewed interest in painting resulted in the rise of a few graffiti artists to art-star status. Jean-Michel Basquiat, a former street-artist known by his "Samo" tag, and Keith Haring, a professionally-trained artist who adopted a graffiti style, were two of the most widely recognized graffiti artists.
More recently graffiti art has resurfaced in a far more overtly politicized form in the subvertising and culture jamming movements and practitioners such as Alexander Brener. Other graffiti artists like Banksy are more ironic in their use of political imagery, who recently accepted a commission from Greenpeace and offers pieces for sale.
Note: graffiti is the plural of graffito, but the singular form is rarely heard.
If you want to know the results from 250 years of graffiti-research spanning 50 000 years of human visual-sign development) from last 26 years use the URLs listed below.