Every country has its own cultural history, human relations, economic relations, political system. Although countries are different, all human beings have basic needs like food, air, water, vehicles, jewelry, computers, paper, books, buildings, metal tools, medicines, shoes, motors, pens, paints, spectacles, fertilizers, airplanes, etc. But not all goods are made in all countries, at all levels, in all seasons. Give and take is necessary.
Some goods and services manufactured in India are needed by America, and equipment and services produced in America are needed by India. Today we give some things to America and take a token as a sign of it because the barter system where we give our thing and exchange theirs at the same time has problems.
Tomorrow I can give them the same token and take their stuff. The value of a table is not the same as the value of a cell phone because the value of things is created by human labor. So the number of tokens depends on the commodity being exchanged. Thus barter becomes necessary not only in different countries but also in the same country by different people. So tokens are needed both internationally and nationally.
Those tokens are called currency. Rupee is the standard of our currency. Dollar standard for America and Euro standard for European countries. Gold has been chosen as the international standard. Most valuable. So if 10 grams are sold for 30 thousand rupees in our country, 500 dollars in America will get 10 grams.
That means the value of 500 dollars is equal to the value of 30 thousand rupees. In other words, every dollar had an exchange value of 60 rupees at that time. European countries have come together and are using ‘Euro’ universally as an alternative to the different types of currencies in their countries. It is not impossible to use a single currency if all the countries of the world come to mutual understanding.