efinition of an essay
An essay is an extended piece of writing that presents and supports a thesis or proposition. The word "essay" derives from the Latin word "exagium", meaning the presentation of a case. When you write an essay you are making a case for the validity of a particular point of view, analysis, interpretation, or set of facts or procedures.
An academic essay is not a regurgitation of facts. Of course, the facts have to be in the essay and they have to be correct, but the facts are only the first step in essay-writing.
If, in giving the facts, you want to quote from a textbook, use the quote only to support or to illustrate the point you're making. It should be a supplement to your words and ideas, not a substitute of them.