Leeward is the direction downwind from the point of reference. The side of a ship which is towards the island is called as ‘lee side’. The movement of a leeward vessel is less manoeuvrable in normal circumstances as compared to a windward vessel, which is the reason why the former has the right of way over the latter according to the rule 12 of the International Regulations for preventing Sea collisions.
The leeward side is usually the drier side as compared to the windward side, being protected from the prevailing wind by the elevation of the island.
Windward is basically the direction upwind from the point of reference. The movement of a windward vessel is more fluent in normal circumstances than a leeward vessel.
In oceanic islands, leeward and windward nature is a crucial weather or climate defining factor.