As an English student, you will read and write many types of texts such as poetry, prose, biography, autobiography, letters and plays. Each genre has particular features which give them a certain look or feel helping you to distinguish between each type.
Biography, as you know, is a text written about someone's life, with the aim of producing a reasonably factual account (although all biographies demonstrate bias). An autobiography is similar, except that the author writes about his or her own life, presenting a sort of personal history. Autobiographies use first person narration whereas biographies use the third person. Both are written in the past tense.
Letters are different in form and are part of a conversation usually, unless the original recipient of a letter never responds. Because of this feature, letters might use the second person. Sometimes letters are reproduced in biographies and autobiographies, if they are important to the historical account. Some authors of novels also include letters, although these are fictional since they are supposedly written by characters, rather than by real people. This is not as confusing as it sounds - practice makes us into sophisticated readers who can tell the difference between historical letters and fiction, even when genres are mixed in this way.
Plays are intended to be staged, so include lots of information to help the director and actors to perform the script. You wouldn't typically find stage directions in an autobiography!
Sharpen your identification skills by playing this quiz on the subject.