Different countries in the world have different exchange rates. In today's world, the strongest purchasing power is basically the euro, because the exchange ratio between the euro and the RMB is about 1:9 ~ 1: 10. Next, the dollar and these two currencies have super purchasing power, because inflation is taken into account when the currency is issued. After all, the European Union and the United States are typical capitalist countries.
The conversion ratio between currencies comes from the exchange of goods. In the actual exchange process, a sheep can exchange 100 kg of rice, which is common in island A, while a sheep on island B can only exchange 100 kg of rice, so the sheep on island A have stronger purchasing power. If residents of Island A want to go to Island B to buy things, they must exchange them into the currency recognized by the tour guide, that is, use their own monetary units. Because its purchasing power is almost the same only after the currency unit is converted, otherwise a sheep on Island A can only be counted as 10 kg of rice on Island B, so the residents on Island A obviously suffer, and the people on Island B exchange a sheep for 10 kg of rice. The residents of Island A obviously took advantage of this. In order to ensure this international fairness, it is natural to convert it into a certain proportion, which leads to the exchange rate.
Of course, exchange rate conversion is not that simple, and it has something to do with international relations and national foreign exchange reserves. The production capacity of commodities, the degree of scientific and technological development and even the distance have certain relations. There are many factors that affect the exchange rate, so the change of the exchange rate is obviously changing all the time. The way we talk about exchanging goods for proportional currency is just an ancient way to understand the exchange rate.