Anything that gives out light, either:
o Its own light, or
o Light reflected from it.
Such things are called objects.
Images:
An image is formed when:
o Light rays from an object are reflected by a mirror, or
o Light rays are refracted through a lens.
Real Images:
o Formed by the actual intersection of light rays.
o Can be displayed on a screen.
o Example: The image seen on a cinema screen.