Passive margin

Okay little buddy, imagine you're standing by the edge of the playground and the ground below you is like the Earth's crust. Now imagine that a long time ago there was a super big and heavy plate of the Earth's crust called a tectonic plate that was slowly moving away from where you're standing. As it moved, it left a space between you and the plate that's called a passive margin.

This space is like a calm and quiet zone between the land you're standing on and the deep ocean. The land continues to erode and waves still come up to the shore, but for the most part it's a peaceful place.

So, the line between the land and the ocean is called a passive margin, and it's found between a tectonic plate and its neighboring plates. The cool thing is that if you look at a map, you can actually see where all the passive margins are located!