It is indeed frustratingly oversimplified and abstruse, in my view. Space “expanding”: imagine a 10cm ruler (with markings) such that the markings “compress”.

It is indeed frustratingly oversimplified and abstruse, in my view. Space “expanding”: imagine a 10cm ruler (with markings) such that the markings “compress”. Now you have the same ruler but “longer”. That is what is meant by space “expanding “. (in some sense, obviously).