A diffraction grating is an optical device that disperses light into its component colors or wavelengths. It consists of a surface with many closely spaced lines or grooves, which can be made from materials like glass or plastic. When light hits the grating, it bends or diffracts, creating a spectrum of colors similar to a rainbow. Diffraction gratings are widely used in various applications, including spectroscopy, where they help analyze the composition of light from sources like stars or lasers. They can also be found in devices like CDs and DVDs, where the grooves help read the stored information by diffracting the laser light.