An essay is a composition that makes one major argument about an idea or a work of literature.
Two common sorts of essays exist. One is the philosophical essay, which explores whether or not an idea is true. The other is the interpretive essay, which asks what idea a particular book is setting forth but does not inquire whether or not this idea is a true one.
Because both sorts of essays are compositions that argue one main point, both sorts are concerned with argumentation. An argument consists of two parts: premises and a conclusion. An essay also consists of two basic parts: a sentence that declares the conclusion (the thesis statement) and several paragraphs that list and defend the premises (the body of the essay).