What is the left side of a ship called why not use left and right?

Define left side of a ship? Left and right are the sides of the human body and you relate it to the body. The problem is that left and right change depending on which way you are facing.

If you are facing the front of the ship the port side is to your left and the starboard side is on your right. By using port and starboard, you are avoiding confusion when talking to other people.