A camera lens focuses light onto the camera's sensor or film. It determines several important factors like focal length, aperture, depth of field, and image quality. There are different types of lenses including prime lenses with a fixed focal length, zoom lenses that can change focal lengths, and specialty lenses like wide angle, telephoto, and macro lenses that serve different photographic needs. The type of lens used affects how much of a scene is captured and the sharpness and clarity of the final image.