Why is it important that the spongy
mesophyll has gaps or air spaces in it's
layers?

No that answer is wrong. you have written the function of mitochondria in chloroplast and function of chloroplast in mitochondria.

Very hard to understand

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it