Short answers, pulled from the story.
Yugi Mutou is a timid high school student who becomes the host to a mysterious spirit after solving the Millennium Puzzle. This spirit is revealed to be the nameless Pharaoh of Ancient Egypt who lost his memories when sealed inside the artifact.
Konami launched the Yu-Gi-Oh! Trading Card Game in Japan during 1999 based on the Duel Monsters game from the original manga series. By 2011 Guinness World Records named it the best-selling trading card game in history with billions of cards sold worldwide.
Kazuki Takahashi originally planned to draw a horror manga before deciding to use battle as his primary theme. He found it difficult to create something original since there were so many fighting manga already existing and eventually chose to base the series around games.
The first anime adaptation produced by Toei Animation aired for twenty-seven episodes from April to October 1998 on TV Asahi. A second series called Yu-Gi-Oh! Duel Monsters ran for two hundred twenty-four episodes from April 2000 to September 2004 animated by Gallop.
4Kids Entertainment censored the English language release to make it more appropriate for children. Mentions of death or violence were replaced by references to being sent to the Shadow Realm during this process.