A more elaborate explanation of this subject can be found here, on Yu-Gi-Oh! Wiki.

Yugi Muto, a fan drawing.

Yugi Muto (武藤遊戯, Mutō Yūgi) is the main character of the Yu-Gi-Oh! anime series. Many people role-play him on YouTube, such as the people on the channels, YuugiMuto, YugiKingOfCardGames and YugiMotoOfficial. In the anime, he is a young boy who, through solving the Millennium Puzzle, becomes the host of Yami Yugi or the spirit of Pharaoh Atem.