From the official Associated Press website at http://www.ap.org
Founded in 1848, The Associated Press is the oldest and largest news organization in the world, serving as a source of news, photos, graphics, audio and video for more than one billion people a day.
The AP is the backbone of the world's information system. In the United States alone, AP serves 5,000 radio and television stations and 1,700 newspapers. Add to that the 8,500 newspaper, radio and television subscribers in 121 countries overseas...
Basically, the AP is a non-profit organization of news reporters and photographers. It is a newswire, which means that member news organizations may pick and choose from the stories and photographs submitted by AP staff, for a flat subscription fee.
AP stories tend to be as even-handed and unbiased as the mainstream media gets, and occasionally they produce some great investigative reporting. AP staff has won 47 Pulitzer Prizes over the years.