Holographic Principle Projection

Hi. I have a question about the Holographic Principle. I've been looking up things about it for a while now, and I think I understand it. The total content of a space is propositional to the area surrounding it and not the volume. The thing I'm having trouble with is how everything seems 3d. I'm going to assume we are not a projection of light (right?), so how does the "projection" work?



I'm not that good with math or physics so please keep it simple. Thanks.