Port and starboard are nautical terms with origins in Old English. Their meanings are simple: to an observer standing on a boat and facing the front of the craft, port is the left side of the boat, and starboard is the right. If it helps, just remember that port and left are both four-letter words ending in t.
Both adjectives are often used to make the phrasal adjectives port-side and starboard-side, which are hyphenated. Of course, side doesn’t add anything to the words, which already denote sides.
Examples
Once again, the quartermaster turns the wheel hard left to the port side of the ship. [BusinessWeek]
The others joined us. We were seated close by the starboard side of the destroyer. [Shoreline Times]
He is removing covers surrounding the port-side Solar Alpha Rotary Joint to begin applying fresh grease to the ring that allows the power-generating wings rotate and track the sun. [Spaceflight Now]
As our waiter Boyke brought breakfast to us, the beautiful cliffs of Sorrento, Italy, came into view on our starboard side. [The Province]