Star Child
From Multiversal Omnipedia
The Star Child is an immortal energy being that David Bowman becomes- presumably the final result of Mankind's evolution, the grand result of the Firstborn's plan. Man will evolve to the point where he will be free at last; he will be unencumbered by any crude tools or physical forms. He will at last take his place in Eternity.
They also transformed Hal and Dr. Floyd into Star Children, as a favor for Bowman.