Graffiti, like any other form of art, has its own history. The word can be traced back to the Roman Empire and translates loosely into "writing on the wall". It was until the 20th century, around the 70's, where modern day graffiti started to take form. It evolved to getting bigger and more artistic. The size started to increase as the creators started to out-do one another. The bigger the name was, the more bragging rights you had and the more important it became. There was almost an unspoken competition between the artists.
I use the term artists because they are, in fact, artists. Graffiti is highly under appreciated and over-looked due to the fact that it is illegal and usually located in places that are run-down. In actuality, it takes tons of practice in order to make it look good. A lot more thought is put into it than we think. It's not just some kid walking up and spray-painting a wall. It also isn't easy since it's not as if they can practice it willingly; they have to dodge cops and property owners. If caught, they face large fines or even jail time.
Unfortunately, the name "Graffiti" gets a bad feeling from it since it is associated with illegally defacing public property, even though there are some really incredible works of art that fall under the category. The work can actually be poetic and beautiful since there can be a lot of emotion, depending on the time/mood it was created. There is always a debate over whether something is real "Graffiti", or an artistic work created by a professional artist.
Are legal murals graffiti, or does it have to be illegal and unpaid? Typically this depends on a persons view towards graffiti. In most countries, however, artwork labeled as graffiti is usually illegal.
Good or Bad Graffiti?
Graffiti work done by TheZork
GRAFFITI IN DESIGN
"This Is Not Graffiti"