Final answer:
The key difference between a biography and an autobiography is the author's relationship to the subject; biographies are about others and require more research, while autobiographies are self-written personal narratives.
Step-by-step explanation:
A key difference between a biography and an autobiography is The author's relationship to the subject. A biography is a narrative about someone else's life written by an author, who conducts research and may need to infer motivations from actions if no direct information is available.
In contrast, an autobiography is written by the subject about their own life, meaning they have direct knowledge of their thoughts, feelings, and motivations, and less inference is required. An autobiographical narrative is inherently more personal and provides a direct insight into the author's experiences and personal growth.
When writing a biography about someone who is not well-known to the writer or who is no longer living, the author needs to suggest motivations by analyzing actions and available historical evidence or documents. Autobiographies, meanwhile, offer a first-hand account of events and the personal reflections of the author, making them naturally more personal in nature.