Cataract is where the lens inside the eye becomes cloudy. The lens is responsible for focusing light onto the retina at the back of the eye. Think of the lens inside the eye as being a clear window to look through. When cataracts start to develop it can be like looking through a frosted window. Most people complain of "misty" or "filmy" vision and colours can appear faded.
In the early stages of cataract, new spectacles may improve vision, but as the cataracts worsens, cataract extraction may be required to remove the cloudy lens and an artificial lens inserted in its place.