The main sail is the largest sail on a sailing vessel, typically attached to the main mast. It plays a crucial role in harnessing wind power to propel the boat forward. The shape and size of the main sail can vary depending on the type of boat and its intended use, such as racing or cruising. When sailing, the main sail works in conjunction with other sails, like the jib, to optimize performance. Adjusting the main sail's angle and tension helps control the boat's speed and direction. Proper handling of the main sail is essential for effective sailing and safety on the water.