when you have a pc case with the glass side that shows no light inside its like a black shell.
Now you have a light source shine light on something outside the pc case facing the glass on the side of the pc case, not you look at the image of the thing being lit up by the lamp and you see a hologram.
to recreate this using a video source its done the same way, have a glass over a black box. cast light on some image and the image if its stereoscopic and moves when the person moves their head looks stereoscopic on the glass.
Now have a glass on top of that you might need a box to lift the glass over the black background.
Now put something in front of the glass, like a cup, or a statue, now put a light source in-between the glass and cup/statue so the glass shows a picture of the cup/statue.
This is a hologram! Now to see around the cup just move your head around the cup/statue to see the different viewpoints of the hologram.
