Solar sails use light particles (photons) to push them across space, much the same way boats use wind in their sails to push them across the water. Solar sails are large and therefore must be folded up for launch and unfurled in space.
Though the concept has been around since at least the 1800s, the first successful solar sail mission began in 2010 with IKAROS, launched by the Japan Aerospace Exploration Agency. Since then, other successful experiments and missions have been carried out by several nations and organizations.
Video: "Solar Sailing with Bill Nye," 2020.