Désert/déserte means that there are no living creatures. Ex : La place du village est déserte à cette heure tardive. (there is no one) Vide = empty; a container is empty. Ex : Le verre est vide. If I say that a room is "vide", it usually means that there are no furniture. If I want to say that no one is in the room, I will probably say: Il n'y a personne dans la salle. or : La salle est déserte (but that's a bit weird for a room).