Sail power refers to the use of sails to harness wind energy for propulsion, primarily in boats and ships. By capturing the wind in large fabric sails, vessels can move across water without relying on engines or fuel. This method of transportation has been used for thousands of years and is still popular in recreational sailing and some commercial shipping. The effectiveness of sail power depends on various factors, including wind speed, sail design, and the vessel's hull shape. Different types of sails, such as mainsails and jibs, can be adjusted to optimize performance in changing wind conditions, making sailing both an art and a science.