Port means the left side of the boat, as you face forward. The opposite of port is starboard. Note that port and starboard are not synonyms with left and right; port and starboard only refer to the sides of a boat and are irrespective of the direction that you or anyone else is facing.
Port used to be called larboard, but it was changed in the 19th century because it sounded too much like starboard. It is called port because that is the side of the boat that is traditionally used to dock. Many ships (and planes) today are configured for easier docking on the port side.