A descriptive quote is simply a quote that throughly describes and gives details about a subject or in this case a character.
Without more information on your assignment, my best understanding is that your teacher is looking for a quote from whatever literary piece you are reading that best describes each of the characters.
After hearing the raucous, cheering response to Adam’s speech, Mr. James feared that his new student body president might be an amateur demagogue.
Angrily, Hamlet denies having given her anything; he laments the dishonesty of beauty, and claims both to have loved Ophelia once and never to have loved her at all. Bitterly commenting on the wretchedness of humankind, he urges Ophelia to enter a nunnery rather than become a “breeder of sinners” (III.i.122–123).
