It’s good to know what your point is. What’s your reason for being here, your reason for writing? What situation caused you to put pen to paper (or finger to keyboard)? What’s your purpose? (Other than a grade in English class, that is…) This concept of purpose is key in rhetoric—and in most communication, really.

The purpose is generally represented as the primary or most prevalent claim put forward in a text; the major idea or thesis an author is arguing. The main claim of an essay, especially an academic essay written for an audience in the U.S., is almost always stated explicitly in a "thesis statement" in the introduction or conclusion, though in some academic writing it is instead stated implicitly through development and support.

There are many genres of writing that do not have a traditional, academic thesis—but do they have a purpose? (I hope you'll note that the answer is almost always yes!)