Each grader is given a set of scoring rubrics similar to this. An understanding of this should help you to see what the graders are expecting to see:
A The "A" essay has a clear central idea that relates directly to the assigned topic. The essay has a clear organizational plan. The major points are developed logically and are supported with concrete, specific evidence or details that arouse the reader's interest. The essay reveals the writer's ability to select effective, appropriate words and phrases; to write varied, sophisticated sentences; to make careful use of effective transitional devices; and to maintain a consistent, appropriate tone. The essay is essentially free from mechanical errors, it contains no serious grammatical errors, and the ideas are expressed freshly and vividly.
B: The "B" essay has a clear central idea that relates directly to the assigned topic. It contains most of the qualities of good writing itemized above. The essay generally differs from a "A" in that it shows definite competence, but lacks distinction. The examples and details are pertinent, but may not be particularly vivid or sharply observed; the word choice is generally accurate, but seldom -- if ever -- really felicitous. The writer adopts an appropriate, consistent tone. The essay may contain a few errors in grammar and mechanics.
C The "C" essay meets only the basic criteria, and those in a minimal way. The essay has a central idea related directly to the assigned topic and presented with sufficient clarity that the reader is aware of the writer's purpose. The organization is clear enough for the reader to perceive the writer's plan. The paragraphs coherently present some evidence or details to substantiate the points. The writer uses ordinary, everyday words accurately and idiomatically and generally avoids both the monotony created by series of choppy, simple sentences and the incoherence caused by long, tangled sentences. Although the essay may contain a few serious grammatical errors and several mechanical errors, they are not of sufficient severity or frequency to obscure the sense of what the writer is saying.
D/F: The '"D/F"' essay has any one of the following problems to an extraordinary degree or it has several to a limited degree: it lacks a central idea; it lacks a clear organizational plan; it does not develop its points or develops them in a repetitious, incoherent, or illogical way; it does not relate directly to the assigned topic; it contains several serious grammatical errors; it contains numerous mechanical errors; ordinary, everyday words are used inaccurately and unidiomatically; it contains a limited vocabulary so that the words chosen frequently do not serve the writer's purpose; syntax is frequently rudimentary or tangled; or the essay is so brief that the rater cannot make an accurate judgement of the writer's ability.
If you see a word you don't understand....LOOK IT UP!