Directions on the water can be described in terms relative to the wind, or relative to 'left' and 'right.'
The direction from where the wind is blowing is windward. The direction away from where the wind is blowing is leeward. To change one's direction to point more toward the wind is to head-up. To change one's direction to point more away from the wind is to fall-off.
If the wind is coming over the right side of a ship, therefore the sailor' right hand is forward, the ship is on starboard tack. If the wind is coming over the left side of a ship, therefore the sailor' left hand is forward, the ship is on port tack.