Z scaling

Can anyone tell me what scaling along the Z axis actually does. I can see what X and Y scaling does and scaling all of them X, Y and Z but I don’t know what scaling along Z actually does on its own. Sorry if this is a bit basic but we all have to start at the beginning.
Thanks for any replies.

scaling along z axis doesn’t do anything else than scaling along x and y axis.

imagine you draw a cube around the origin with vertex coordinates at
(-2,-2,2); (2,-2,2); (2,2,2); (-2,2,2) for frontside
(-2,-2,-2); (2,-2,-2); (2,2,-2); (-2,2,-2) for backside

now if you would only scale along x and y axis by 2 you would get something like
(-4,-4,2); (4,-4,2); (4,4,2); (-4,4,2) for frontside
(-4,-4,-2); (4,-4,-2); (4,4,-2); (-4,4,-2) for backside

now you don’t have a cube any more, so it’s necessary to scale the z axis also, because otherwise you loose your length ratio of your sides.

hope that helps a little