What is meant by “purpose” in an essay?
In essay writing, a purpose is what you hope to accomplish with the essay. Do you want to inform, to persuade, to describe, to argue, to entertain, to compare? If you are sure about your essay’s goals before you begin writing, you can more accurately organize and write your essay. Why are you writing?
In English Composition I, purpose usually refers to the writer’s position on a subject: an assertion, point of view, or argument about the subject that the essay will address and support. An essay’s purpose should be made clear by the title and thesis statement.
Does the writer have an opinion and will it be presented in the essay? No, there’s nothing wrong with an exploratory essay if that is what your professor assigned, but generally college-level essays will require you to make an argument and support that argument about a particular issue. For further discussion of purpose, see What is a “thesis statement” and how do I write a strong one?