1. to put down on the ground (Something that was on a table for instance, implies a certain weight. Only works with "runter".)
2. to turn down (In a sense of lower, but not off. The main use I can think of is a heater or a stove, but it's not useful beyond that. Can work with "herunter" and "runter")
3. to put something "under it/that" (The focus is on the fact that the object then stands under whatever it is for a while, so the stationary part matters. That's why only "drunter" is really idiomatic. "runter" kind of works, "herunter" not at all.)
