Say it like this

Going round and round something because it keeps pulling you in and you keep missing it.

For the grown-up

An orbit is the curved course one body follows around another under gravity. The elegant description is that an orbiting object is falling continuously and moving sideways fast enough that it never arrives.

The easy mistake

Careful here. Nothing is holding the moon up. It is falling, permanently, and missing. That framing is both correct and considerably more memorable than the usual one.

Words next to this one

Gravity The pull that everything with weight has on everything else. Bigger things pull harder. Star An enormous ball of burning gas, so far away it looks like a dot. Our sun is one. Galaxy An enormous group of stars travelling together. Ours has a couple of hundred billion in it. Universe Everything there is, including you. Most of it is empty space.