A keel is a structural component of a ship or boat that runs along the bottom from the bow to the stern. It provides stability and helps the vessel maintain its balance in the water. The keel is often considered the backbone of the ship, as it supports the hull and can affect the vessel's performance and handling. There are different types of keels, including fin keels, full keels, and bulb keels, each designed for specific purposes and types of vessels. The design and shape of the keel can influence how well a boat sails, its speed, and its ability to resist capsizing in rough conditions.