Dance Dance Revolution, or “DDR”, is a rhythm game franchise created by Konami. It first launched on November 21, 1998 in Japan.
Gameplay consists of one or two players standing on pads with arrows corresponding to Left, Down, Up, and Right. The player selects a song and difficulty they wish the play, and then must step on the appropriate arrow on the pad as the pattern on the play screen scrolls up to a set of arrow cursors on the top of the screen.
Additional information related to the DDR franchise can be found at the DDR Wikipedia article.