Magnification of image is defined as the ratio of height of the image to the height of the object. Mathematically, 

m = \(\frac {height\:of\:image\:(I)}{height\:of\:object\:(O)}\)

Real image is defined as the image that can be obtained on a screen. It is formed by the actual intersection of the refracted rays in a convex mirror.

Virtual image is defined as the image which cannot be obtained on the screen. It is formed by the intersection of the rays in a concave mirror or lens.

S. No. Real Image S.No. Virtual Image
1. It is formed at that point where the refracted rays actually meet. 1. It is formed at that point where the refracted rays appear to meet.
2. It is always inverted. 2.  It is always erect.
3. It is always formed on another side or behind the lens. 3. It is always formed on the same side where the object in the lens is.
4. Its size depends on the distance of the object from the optical centre of the lens. 4. Its size varies in concave and convex lens. It is larger in convex lens and smaller in concave lens.
5. It is obtained on a screen. 5. It cannot be obtained on screen.