Suppose you had two entangled particles light-years distance apart.

Observer A observes one entangled particle at a spin up. At the same time, Observer B observes particle B at a spin down.

Observer A's observation of a spin up means observer B must see a spin down. However, the two observers are restricted at the speed of light to communicate this to each other.

It would initially seem like there is a instantaneous causal impact based on observer A's observation. But that's not the case.

I tend to think it was predestined what each observer see, but that leads to all sorts of philosophical questions.

I hope I did this topic justice, I find it quite interesting but have no background in it.