Quick AnswerUK students mainly write argumentative, analytical, expository, reflective, narrative, descriptive and compare-and-contrast essays. Each has a different purpose and is marked differently, so identifying the type tells you what kind of writing the task requires.
Knowing your essay type is the first step to answering the question well. An expository essay that argues a strong position, or an argumentative essay that only describes, will both lose marks. Here are the main types and what each one wants.