Who is Ged or Sparrowhawk from Tehanu: The Last Book of Earthsea and what is their importance?

Sparrowhawk (Ged) was once a young man and prentice of Ogion, the Mage of Gont. He trained to become a mage like Ogion, and after many adventures, he became the Archmage of Roke.
Sparrowhawk's true name is Ged.

While still a young man, Ged went on an adventure with Tenar, in which, they brought the Ring of Erreth-Akbe back to its place in Havnor. Tenar then became his prentice. Tenar, however, turned her back on that life. After losing his powers, Ged returns to her as a sick and depressed man, unable to define himself without his powers.