Essays are one of the most common types of nonfiction. They can be either formal (serious and objective) or informal (more personal, often intending to entertain or persuade the reader.) Academic and personal essays are common types of the genre. Textbooks and user manuals can generally be thought of as a collection of formal essays as well.
Journalism is the branch of nonfiction that deals with the reporting of events and trends. Like essays, journalism can deal strictly with facts or it can be opinionated. Newspaper, journal and magazine articles and columns are common examples of journalism.
Biographies are the story of a specific person's life. Biographies are written to show the uniqueness of an individual's life while still drawing forth certain universal life experiences. Attention is paid to detail and accuracy in biographies. An autobiography is a type of biography written by the person whose life is being chronicled in the book. Autobiographies give the reader insight into the author's personal evaluation of his life. Memoirs are basically specialized autobiographies that focus on a specific point in the writer's life.
Journals and diaries are similar to autobiographies or memoirs in that they chronicle a person's life (or part of it) from her point of view, but they are usually more personal than biographies because they are not intended to be published.
Historical nonfiction tells the true stories of historical events. This type of nonfiction involves a great deal of research and investigation. As with other forms of nonfiction, great care is taken to weed through inaccuracies and only publish facts.
Direct written correspondence between two or more people is considered a type of nonfiction. Letters often contain personal information and can often give the reader insight into the type of person the author is or was. Letters are often published in biographies or as appendices to novels or other popular books.
Speeches and sermons are some of the most treasured pieces of nonfiction. Lincoln's "Gettysburg Address" and Martin Luther King's "I Have a Dream" speech are two enduring examples of famous oratory pieces that have been transcribed and reproduced countless times.