A biography is the story of a person's life in the words of another person, while an autobiography is the story of a person's life in his own words. A biography is typically written in third person, while an autobiography is typically written in first person.
In addition, there are different levels of subjectivity in autobiographies than there are in biographies. In an autobiography, all events are recounted as they were experienced by the author. This allows the author to give readers a better sense of his persona and language, but it also means that the author may not be able to be trusted for a completely unbiased opinion. A biographer, on the other hand, is much more likely to be objective because he is basing the work on extensive research performed on the subject of the book and not personal opinion.
In an autobiography, the writer is able to directly address and speak to readers in a way that seems immediate and real. However, this only allows the reader to see the person's life from one view, which may be skewed. A biography offers many more viewpoints of the person that it covers.
While an autobiography is usually written by the subject instead of another writer, some individuals hire a writer to assist with the document. Usually, this results in a dual by-line that includes both names.
Some of the most famous autobiographies include "The Diary of a Young Girl" by Anne Frank, "Night" by Ellie Wiesel and "Long Walk to Freedom" by Nelson Mandela. Famous biographies include "Steve Jobs" by Walter Isaacson, "John Adams" by David McCullough and "Team of Rivals: The Political Genious of Abraham Lincoln" by Doris Kearns Goodwin.