What is the name of a person who writes essays?

As a writer, I would definitely say describing a person in an essay depends upon what class and the teacher, otherwise it's totally up to the writer. Even though you're not using various colors or textures typically when you write, it is a form of expression. There are rules to be applied as far as the grammatical, etc., but when you're expressing yourself, there is no steadfast criteria for that.

If writing an essay, try focusing in on each of your senses. What does the person look like, sound like, smell like, or even taste or feel like. You can use adjectives to describe each of these. An example might be "The old woman smells like moth balls released from a closet of wool where they've been stored in the back corner of the closet past their expiration date." Using smell again, you can paint a picture of beauty, "Stepping onto the balcony, the cool wafts of saltwater fill my nostrils with a refreshing spray of misty morning air."

If you want to get really creative, you can describe what emotions are stirred in addition, especially when you use the sixth sense--thought.