ELI5: Explain Like I'm 5

As above, so below

As above, so below means that whatever happens on one level of things can also have an effect on other levels too. It's like when you drop a stone into a still pond and you see the ripple effect. The stone dropping is causing the ripples, but the ripples can also be seen in the sky above as concentric circles when looking at clouds. Just like the dropping of the stone, certain things happening in our lives, such as thoughts and actions, can have an effect on both what's happening around us and what's happening inside us.