A port tack in sailing occurs when the wind blows over the port (left) side of the boat, causing the sails to fill on the starboard (right) side. When on a port tack, the boat's boom is positioned on the right side, and it must give way to boats on a starboard tack, according to navigation rules.

Key Aspects of a Port Tack:
Wind Direction: The wind strikes the port (left) side of the boat.

Sail Position: The mainsail and boom are on the starboard (right) side.

Rules of the Road: A vessel on a port tack must "keep clear" (give way) to a boat on a starboard tack.

Distinction: It is the opposite of a starboard tack, which is used to determine right-of-way in racing and general navigation.