Magento currencies scope.

I’m reading on the difference between Website, Store and Store view.

All are clear, or at least becoming clear, reading more about those and the documentation, except one.

I don’t understand the concept of currencies being different at the Website level, then same on the Store level and then again different at the Store view level?

How would a store that only accepts euros, be able to have 2 store views one accepting Dollars and another accepting Polish zloty, for example?

I haven’t been able to find a resource that explains this at all.

Any guidance would be greatly appreciated.