Paper money, or best known as bills, were used for the first time in China, in the 9th century. And the travels of Marco Polo, introduced the idea of paper money to Europeans, so in Europe,bills appeared in the 13th century. And, in 1946, the first credit card was invented.
Before money (bills and coins) appeared, bartering was used instead of money to buy goods. Many things have been used as medium of exchange in markets, for example, livestock, sacks of cereal grain, gold, precious metals (from which early coins were made) and others. Besides, money (coin) is made of steel covered by copper, nickel and brass.
So, we can see that money has changed a lot through history, and it's still changing. For example, maybe in the future we will use credits cards instead of paper money and coins. That's a possibility.
This a video that explains the history of money through the years.
