Real image | Virtual image | Erect image | Inverted image
Real image: The image formed by direct convergence of light when the outgoing light is converging. (Note: A real image can be intercepted by a surface.)
Virtual image: The image formed by direct convergence of light when the outgoing light is diverging. (Note: A virtual image cannot be intercepted by a surface, but can be perceived by the human eye or converted into a real image by another converging system.)
Erecting image: An image that is aligned with the object's up-down and left-right orientation.
Inverted image: An image that is opposite to the object's up-down and left-right orientation.
Image rotation
Image rotation: The use of optical elements to rotate the image relative to the object.