Final answer:
The left side of a boat is called the port side and is indicated by a red light.
Step-by-step explanation:
The left side of a boat is called the port side. The term 'port' refers to the left side of the boat when facing forward. It is named as such because the left side was traditionally the side of the ship where cargo was loaded and unloaded in ports.
The light used on the left side of a boat is a red light. This is known as the port navigation light. It helps other boaters determine the direction and location of your boat at night or in low visibility conditions.
It is important to remember that navigation rules may vary depending on the country and the type of vessel. Always refer to the appropriate boating regulations and guidelines in your area.