Light sails are a type of spacecraft propulsion that uses the pressure of sunlight to propel a vehicle through space. These sails are made of large, reflective materials that capture photons from the sun. As photons bounce off the sail, they transfer momentum, gradually pushing the spacecraft forward. This technology is being explored for various missions, including potential travel to distant planets and even interstellar exploration. Projects like Breakthrough Starshot aim to develop light sails that could reach speeds up to 20% the speed of light, allowing for faster journeys across vast distances in the universe.