On avenue under the grades tabs it says "dropped" under one of the essays I had to write for the course. What does that mean?

they aren't counting the mark to your final, usually it is your lowest mark in that category

Yeah, they did that for Philosophy 2tt3, too. We only had to write 1 out of 2 essays, but were given the option to write both in case we didn't like the mark we got on the first one. Eventually, your lowest essay mark gets 'dropped'. It's a good thing; it ultimately raises your average.