It means you need to know what your professor expects in the paper, and how the assignment fits in with the entire course and its grading structure. This writing course requires peer review, multiple drafts, careful copyediting and getting the work done on time. Chances are you will have no other course in which the teacher schedules these for you and helps to show you ways to write toward clearer thinking and correctly edited English prose. You will have to do that on your own now. Here's How You Can.
Some teachers believe it is improper for academic writing.
Some teachers object to an 'everyday' voice, and require a more formal detached tone. If the answer is yes, do not assume you can rush a draft in the night before. Some teachers will do this. These are good ways to get to know what your teacher looks for. Sometimes, when you are writing about new information, you may lose your confidence and you writing might crumble.