I would like to understand in atomic terms what makes the value of one nation's currency change with regard to another. Read that, without citing complex terminology but in basic terms.
Obviously, if one nation does QE then it would follow that the value of that currency is devalued by the ratio of "easing" to the existing supply.
But in all other cases, suppose you have nation A and nation B and their currencies are initially 1-to-1. What would make nation A's currency be worth more than nation B's currency, and what is the rationale behind it?
So for example, nation A becomes more efficient in manufacturing than nation B; but how would that make the currency of nation A worth more? Efficiency is the only answer that comes to mind, so I appreciate further elaboration and hope this question has educational value.