If you don't mind, I'd like to know more about this and how it works. Feel like writing a few more paragraphs?
Sure! The easiest way to look at it is that exchange rates represent supply and demand for currencies on the international markets.
If people in the US buy something made in China, we are in effect sending dollars to China (and the international exchange market). This increases the supply of dollars that are available internationally. Supply and demand (broadly) says that the greater the supply relative to demand, the lower the price.
Now imagine two countries that have a 1:1 exchange rate at the start. To buy a widget built in country A costs $1 as does buying a widget built in country B. Say country A has a big trade deficit with country B. That means there are a lot of CountryABucks floating around the world and they lose value. Now the exchange rate is 2:1. That means that although the cost of building a widget internally in each country has stayed the same in terms of labor, materials, etc, if country A's citizens were to buy an imported widget from country B it now suddenly costs them $2 instead of the $1 if they bought a domestic widget. That price differential depresses demand for country B's widgets and (all other things being equal) works to eventually balance trade back out.
This is one of the big reasons why China is buying a lot of things in the US, to attempt to counteract that effect. Japan did the same thing in the 80's. In this case Germany didn't have to do that however, as they are part of a monetary union with the Euro. That means that no matter how bad the balance of trade gets there isn't a possibility for currency value changes to even it out.
