A biography is the life story of a man or woman written by someone else. Such a book is usually undertaken because of the interest of the author in that person. An autobiography is when a person writes their own life story.
Ferdinand Megellan - without me looking him up on the Internet and just going from memory - was a Portugese explorer way back in the 1500s. He was, if I'm recalling this right, the captain of the first ship which ever sailed right around the world. He didn't make it, dying at sea when the ship was on the way home. But he had a lot of places around the world named after him, including the Straits of Magellan at the southern end of South America. A ship could but through here without going right down to the very south around Cape Horn.
Hope this helps.