Dungeons & Dragons

The first Dungeons & Dragons game was played back when Gary Gygax and Dave Arneson chose to personalize the massive battles of their fantasy wargames with the exploits of individual heroes. This inspiration became the first fantasy roleplaying game, in which players are characters in an ongoing fantasy story. This new kind of game has become immensely popular over the years, and D&D has grown to include many new ways to vividly experience worlds of heroic fantasy.

The core of D&D is storytelling. You and your friends tell a story together, guiding your heroes through quests for treasure, battles with deadly foes, daring rescues, courtly intrigue, and much more. You can also explore the world of Dungeons & Dragons through any of the novels written by its fantasy authors, as well as engaging board games and immersive video games. All of these stories are part of D&D.

From http://dnd.wizards.com/dungeons-and-dragons/what-is-dd