who is he?

Santa Claus, St. Nicholas, Father Christmas, Kris Kringle, or simply Santa, is a legendary gift-giving icon who distributes presents to sleeping children and adults who have been "good" all year; traditionally during the night of December 24, Christmas Eve. The popular American form Santa Claus originated as a mispronunciation of Dutch Sinterklaas, which is a contracted form of Sint Nicolaas (Saint Nicholas). Father Christmas is a well-loved figure in many countries and predates the Santa Claus character. Father Christmas is similar in many ways, though the two have quite different origins. Using 'Santa' in places that predominantly call him Father Christmas may be viewed as an Americanism, although they are generally nowadays regarded as the same character. You can find information on wikipedia.