OK can you explain kernels and their role in transformations (f.e. the dimension formula)? No you can't this way. And it truly has an INTUITIVE explanation (so much more than the intuitive ess of a spreadsheet!).
This is the first, simplest, off-hand example I can come up with.
Things are blocked "in parallel" (assuming the camera is far away from the objects) because that projection is a linear map (I repeat, assuming "far away focus") and has a one dimensional kernel: 2d + 1d = 3d, which means (flat TV + orthogonal lines = 3d world), that is the dimension formula.