Overview
The bow is the forward part of the hull of a ship or boat, the point that is usually most forward when the vessel is underway. The aft end of the boat is the stern.
Prow may be used as a synonym for bow or it may mean the forward-most part of the bow above the waterline.
Function
A ship's bow should be designed to enable the hull to pass efficiently through the water. Bow shapes vary according to the speed of the boat, the seas or waterways being navigated, and the vessel's function. Where sea conditions are likely to promote pitching, it is useful if the bow provides reserve buoyancy; a flared bow (a raked stem with flared topsides) is ideal to reduce the amount of water shipped over the bow.
From Wikipedia (CC BY-SA 4.0).