When light rays fall on a mirror - convex, plane, concave - they get reflected back in to the medium. If many rays that emanate from one point on the object fall on the mirror and then converge towards a point, then a real image is formed. This image can be projected on to a screen.
If many rays that emanate from one point of object after reflection appear to diverge from one point (on the other side of mirror), then we say a virtual image is formed. This image can be only seen by the eye. Eye understands and feels the virtual image. But actually there is nothing at the location where virtual image seems to appear.
The plane mirror in bath room or make up room shows us virtual images. But you can take a mirror to reflect the light coming from a tree and project it onto a white wall. If the wall and the room are dark, you may be able to see some images of distant objects there.
In lenses and telescopes, microscopes real and virtual images are formed.