Why did coins replace other mediums of exchange

Coins were developed as a medium of exchange because they are easy and more convenient in negotiating and purchasing. For example, the British pound, the yen, and the euro are examples of currencies. It is letter A. Currencies are the money used in a certain country in their everyday purchase of goods inside the country. When a person goes to other country and exchange his or her money for another money that can be used inside the country he is now currently in, then that is exchanging rates. Tariffs are the taxes payed by a certain company of exporting or importing industry to transport it from one place or country to another country.