You are referring to Rubeus Hagrid played by Robbie Coltrane.
Hagrid is a Half-Giant (father is human, mother is giant; Fridwulfa) and gentle as a lamb, unless you insult headmaster Dumbledore in front of him.
He entered the story almost immediately as a mentor-figure to Harry and his friends. In the first book, Rubeus Hagrid is the one who retrieves Harry from his Aunt and Uncle, informs Harry that he is a wizard, gifts Harry with the boy's beloved snowy owl, Hedwig.
Check out these 27 mind-blowing "Harry Potter" movie facts that'll make you want to watch them all over again (again) shared by Seventeen.com.