A biography details a person's life, while an autobiography is a biography written by the person discussed in the work. Many of the world's greatest works of literature are autobiographies, including Julius Caesar's "Commentaries," Benjamin Franklin's "Autobiography," and the early portions of St. Augustine's "Confessions of St. Augustine." The modern personal biography began in 15th century Europe, perhaps with Margery Kempe, an English religious mystic.
Advantage: Inform Readers
Authors use autobiographies to not only to share events that occurred in their lifetime, but help future generations relate to those events by explaining their affect on the lives of those who lived through them. This has the advantage of personalizing historical events. For example, it's one thing to read about the civil rights movement in the abstract; it's entirely another to read firsthand accounts, especially from those who benefited from the changes.
Advantage: Persuade Readers
An old adage says: "Don't judge a man until you've walked a mile in his shoes." Autobiographies allow readers to walk, so to speak, in the shoes of someone else and come to understand his motivations and behavior. The "Autobiography of Malcolm X," for example, recounts his childhood, criminal past, and religious journey and has softened attitudes toward his legacy.
Because an author may write an autobiography with persuasion in mind, readers often regard autobiographies skeptically. This is a major disadvantage of the genre. Readers may feel that an author's true purpose in writing is to persuade, perhaps be embellishing or even lying, rather than to inform. Some authors may misrepresent facts inadvertently because they wrote many years after the events being detailed occurred.
Disadvantage: Judgment of History
Bernal Diaz de Castillo wrote "The Discovery and Conquest of Mexico" to entertain and inform his readers. His autobiography, however, details his participation in a war between Spain and its indigenous allies and the Mexican empire and its allies. Many of the events that occurred, such as the destruction of ancient Mexico City, subject him to criticism from modern readers who find his actions repugnant. All autobiographical writers face the possibility that future generations may judge them from a different perspective than expected.