Real images versus virtual images – convex lens

The main difference between a real image and virtual image is

A REAL IMAGE CAN BE DISPLAYED ON A SCREEN

A real image can be displayed on a screen or piece of paper or on a wall, whereas a virtual image cannot.

Fish watching a real image being displayed on a screen

A virtual image can be seen with the eyes but it's impossible to display the image on a screen.

When the object is beyond the principal focal point in front of the lens, its light rays can be projected and focused on a screen. If the screen is moved anywhere else, it will be blurry.

Ray diagram of a real image inverted on a screen

Whereas, if the object is between the convex lens and the principal focal point in front of it then a virtual image can only be seen by your own eye. It can not be collected or shown on a screen.

Ray diagram of a virtual image seen through a convex lens

Notice, too, that with lenses

REAL IMAGES – ALWAYS INVERTED

VIRTUAL IMAGES – ALWAYS UPRIGHT

A real image is always inverted whereas a virtual image is always upright.