After a breakdown and a build-up of rising tension, the drop releases everything at once: the kick, the bass and the main hook. In EDM it is the peak of the track; in dubstep and trap, the drop is where the bass design takes over.
Many drops are preceded by a short silence or a single beat of space, which makes the impact feel bigger.
Using it in a prompt
Describe the drop ("supersaw drop", "heavy bass drop") and when it happens ("drop at 0:45") for edits that cut on the impact.