Some essays are You're also going to have to learn that person's entire life story, because that's what a biography is supposed to be.
An essay should include an introductory paragraph, a body of three or more paragraphs, and a conclusion. A thesis statement that describes the main point of an essay should appear in the introduction and body paragraphs should have topic sentences that relate back to and expand on the thesis statement. Narrative essays may be biographical in nature, and even expository essays can be biographical if they present factual information about another person's life, but most biographies are much longer than any traditional essay.
A biography should include all of the important or interesting stories of a person's life. Biographies usually begin with a person's birth and the details of their childhood before recounting the significant moments the subject of a biography experienced throughout their adult life.
Published biographies are usually about a person who is famous, such as a president or other world leader, an actor, or an activist. At least some reflection by the writer on how the experiences of their subject's life shaped them as a person is also included in a biography, which means a writer will likely have to make inferences about the subject. For that reason, it's important that a biographer have as much information as possible in order to write an accurate account.
Other than the requirement of summing up a person's life, there aren't any set structures or guidelines that must be followed in writing a biography. Some biographies can be written in essay form, some in the form of much longer books, and some are written as movie scripts or plays.
For an essay, you will need to know the relevant facts of your subject. For instance, if you write an essay about a scientific discovery, you should know who made the discovery and when as well as why the discovery is important.
For a biography, you'll need to know all the details of a person's life, such as when and where they were born, which experiences they saw as significant, and how those experiences affected them. At some point, you'll also need to explain what you found interesting enough about the person that made you decide to write a biography of their life in the first place.