talking on basic terms,
A currencey is worth what its economy does..and is mostly pegged to the US Dollar to give it a referance of value.As far a currencies price or value ,, that depends mostly on the markets reactions to economic reports for the country.Good economy stronger currency.The Central bank basicly regulates its currency to either boost its economy or slow it down.Depending on the country,say Japan.....Japan wants a weak dollar because being an export country its economy depends on exporting to other countries mainly the US,they can sell their products cheeper than the US can.So more people will buy a product made in Japan just because its cheeper.So you would think Japans economy has to be doing good so the currency should valuate,but its not ,why? The central bank controls this by buying US tresuries (US Debt.)and by doing this making the dollar stronger.(Stronger dollar weaker Yen)..thats just 1 way.Japan manipulates its currencey by manipulating not its own but our currency.But soon that will stop,and the yen will go up in value.....
Central banks hold in reserve US Dollars mostly but others as well to buy products from the countries they do business with..Remember they need US Dollars to buy OIL.And to buy a product from a foreign country you need to buy it with its currency not yours ...this is where the exchange rate comes into play..
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