which image can be seen by us and photographed simultaneously - real or virtual. I don't understand the major difference between the two.
A real image is one through for which the rays forming the image pass through the point where the image is seen. A virtual image is one where they do not, but projections of the rays do.
In the latter case the rays (the solid red lines) do not actually pass through the image (the larger of the two arrows) only its projections (the dashed red lines) do. Whilst in the real image the solid red lines do actually pass through the image (the arrow on the RHS of the lens).
A real image can be projected onto a screen and can be seen by our eyes. But since the virtual image the rays don't actually converge onto the virtual image it cannot be viewed on a screen but can be seen by our eyes (which act as an additional optical system). In the virtual case the image can only be seen by passing it through a further optical system, in a camera you have such an optical system so both a virtual and real image can be photographed and seen.