Reflectivity occurs when light is thrown or bent back from a surface to create an image.
Either in many angles (diffused reflection) or in a mirror like single direct angle (specular reflection).
Most objects that the human eye can see is due to this scattered light reflecting from an objects surface. This 'scattered light' (diffused) is the primary light source in which humans visually observe. This diffused light allows us to see colours.
Objects such as glass, shiny surfaces, shiny or smooth metals, iridescent or glossy surfaces or objects that emit light themselves, like the sun and lamps, reflect light in a singular angle.