The act of towing.

the act of hauling something (as a vehicle) by means of a hitch or rope; "the truck gave him a tow to the garage"

is a contract whereby one ship moves another. Towage, as opposed to salvage, is a service contract, which does not involve a marine peril, and the consideration is an hourly or daily rate or a lump sum, rather than a salvage reward based on the peril, the work accomplished and the value of the object salved.

Where a tug tows or manouvres a vessel in and out of a berth.

The charge made for towing a vessel.

The price paid for towing.