What is a heaving line?

Answer 1

Heaving line is a relatively light line than can be thrown from aboard a vessel to the shore, to another vessel or from the shore to a vessel.

The heaving line is connected to the actual line/hawser/rope that we wish to transfer between the endpoints but is too heavy to be thrown by itself.

Once the heaving line is transfered, it is used to transfer the heavy line between the two end points.

It is customary to weigh the throwable end of the heaving line to facilitate the throwing process, with a weight, e.g. a 'monkey fist' knot.