Many reports are of something that that looks and acts like a drone, particularly in the initial reports from New Jersey of lights low to the ground and darting around over the treetops. These follow "drone sightings" over military facilities in Virginia in October. This original association became the dominant phrase and is now the easiest narrative for the news media.
Many additional reports since have added to the mystery. In addition to varying sizes and shapes, objects have been said to move and change direction immediately, without slowing down or stopping. They have stayed airborne for extended periods, longer than typical drone flight times. There have been no radar data published, implying the military and FAA can't track them.
No one in authority has identified the objects. It is a UFO mystery.