"The PlayStation Portable (officially abbreviated PSP) is a handheld game console manufactured and marketed by Sony Computer Entertainment. Development of the console was announced during E3 2003, and it was unveiled on May 11, 2004 at a Sony press conference before E3 2004. The system was released in Japan on December 12, 2004, in North America on March 24, 2005, and in the PAL region on September 1, 2005.
The PlayStation Portable is the first handheld video game console to use an optical disc format, Universal Media Disc (UMD), as its primary storage medium. Other distinguishing features of the console include its large viewing screen, robust multi-media capabilities, and connectivity with the PlayStation 3, other PSPs, and the Internet.
Sales of the PSP have (with cyclical exceptions) lagged behind its main competitor, the Nintendo DS. Nevertheless, the console is "the most successful non-Nintendo handheld game system ever sold". After the release of a remodeled, slimmer, and lighter version of the PlayStation Portable, titled Slim & Lite, in early September 2007, sales quadrupled in the United Kingdom the following week and increased by nearly 200% in North America for the month of October. The Slim & Lite had a minor redesign including a new screen and inbuilt microphone, and has since been followed by the PSP Go."
Source: Wikipedia, "PlayStation_Portable", available under the CC-BY-SA License.