Port is the nautical term (used on boats and ships) that refers to the left side of a ship, as perceived by a person facing towards the bow (the front of the vessel). The terms are also used for aircraft, spacecraft, and analogous vessels. The equivalent for the right-hand side is "starboard".
A port buoy is a lateral buoy used to guide vessels through channels or close to shallow water. The port buoy is one that a vessel must leave to port when passing upstream if in IALA area A. If in IALA area B (Japan, the Americas, South Korea, and the Philippines) then the 'handedness' of buoyage is reversed!
An archaic version of the term is larboard. The term larboard, when shouted in the wind, was presumably too easy to confuse with starboard -- both words have two sylables --, and so the word port came to replace it, referring to the side of the ship where cargo is loaded from the port. Another source suggests a different archaic word "portboard" (see starboard for further explanation).
Ships carry a red light on the port side, and a green one one the starboard side, plus a white light at the rear. Several mnemonics, such as "no red port left", are used to remember this.
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