Windward is the direction from which the wind is blowing at the time in question. The side of a ship which is towards the windward is the weather side. If the vessel is heeling under the pressure of the wind, this will be the "higher side"

Leeward is the direction downwind from the point of reference. The side of the ship towards the leeward is its lee side. If the vessel is heeling under the pressure of the wind, this will be the "lower side".