Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

How and why does the exchange rate of a currency change almost everyday?
The basic idea is that money's worth is dependent on what it can be used to buy. The principal driver of monetary exchange (using one type of currency to "buy" another) is that usually, transactions for goods or services in a particular country must be made using that country's official currency. So, if the U.S. has something very valuable (let's say iPhones) that people in other countries want to buy, they have to buy dollars and then use those dollars to buy the consumer electronics from sellers in the U.S. Each country has a "basket" of things they produce that another country will want, and a "shopping list" of things of value they want from that other country. The net difference in value between the basket and shopping list determines the relative demand for one currency over another; the dollar might gain value relative to the Euro (and thus a Euro will buy fewer dollars) because Europeans want iPhones more than Americans want BMWs, or conversely the Euro can gain strength against the dollar because Americans want BMWs more than Europeans want iPhones. The fact that iPhones are actually made in China kind of plays into it, kind of not; Apple pays the Chinese in Yuan to make them, then receives dollars from international buyers and ships the iPhones to them, making both the Yuan and the dollar more valuable than the Euro or other currencies. The total amount of a currency in circulation can also affect relative prices. Right now the American Fed is pumping billions of dollars a day into the U.S. economy. This means there's a lot of dollars floating around, so they're easy to get and thus demand for them decreases. It's more complex than that (for instance, the dollar is also used as the international standard for trade in oil; you want oil, you pay for it in dollars, increasing demand for dollars even when the United States doesn't actually put any oil on the market to sell), but basically think of different currencies as having value in and of themselves, and that value is affected by how much the market wants that currency.