To whom or what does the title, The Kite Runner, refer?

The title of Khaled Hosseini's novel, The Kite
Runner, refers to the sport of kite flying so popular among the people of
Afghanistan. As boys in Kabul, Amir often flew kites, even winning the city's most
important competition. While Amir flew his kite, Hassan served as the kite runner,
following it and retrieving other kites that had been cut by the glass-sharpened string.
It is at the end of this competition that Hassan is sodomized by a group of boys while
trying to retrieve Amir's kite. At the end of the story, Amir trades places, running the
kite being flown by Sohrab (Hassan's son) at their home in California. The title
symbolizes the close relationship between Amir and Hassan--one the son of a wealthy man,
and the other a poor servant boy. Amir's running of Sohrab's kite at the end of the
novel helps to break the ice with the reticent boy and helps to atone for Amir's past
sins against Hassan.