The PlayStation 2 is the successor to Sonys PS1 and was originally released on March 4 2000 in Japan.
It's capable of running PS1 and PS2 games as well as playing DVDs and CDs.
The PlayStation 2 had two versions, the PS2, and the PS2 Core. The only real difference - aside from the smaller size - is that the PS2 Core comes with the network adaptor built in, but does not have an expansion bay to add an internal hard disk drive. In addition, the PS2 Core features slightly faster loading times, a slimmer profile, and a top-loading DVD tray (instead of the sliding tray that the original PS2 used).
Even with the release of its successor, the PlayStation 2 remained popular well into the seventh generation and continued to be produced until January 4, 2013, when Sony finally announced that the PlayStation 2 had been discontinued after 13 years of production - one of the longest runs for a video game console.