> What is the difference between "space expanding" and "things moving away from each other"?
Not an astrophysicist, but I think both are happening.
Space is the medium we live in. It’s the cake in the fruit cake. The fruit wants to stay in the same place, but the cake is expanding which is causing the fruit to appear to move away from each other even though the fruit wants to stay in one place. Same with the universe, space is expanding which is causing objects to become farther apart, even if they could somehow have 0 speed.
But in our universe the planets, stars, galaxies, etc. (the fruit) do have speed. Some are getting closer to us, like the Andromeda galaxy, while many others are moving away from us.
However, given the vast distances and how fast space is expanding (how fast the cake is rising), even those distant objects that want to move towards us are actually moving away from us.
Imagine a swimmer swimming against a tsunami. You can be swimming any direction you want but the power and speed of the tsunami will offset that and dictate where you end up.
Space is expanding at incredible speeds, so it’s quite the tsunami: https://www.forbes.com/sites/startswithabang/2020/06/12/ask-...