In the beginning, people bartered. Bartering is the exchange of goods or services for some other goods or services. The exchange items included bags of rice, wheat, cattle, sheep, pigs and so on. Barter system worked like this, take one bag of rice in exchange for one lamb.
But after a few days, it has become increasingly difficult to store the goods taken in exchange and people started thinking they deserve more than these perishable goods. The selfishness to own the things by themselves and store for their kith and kin has made the man think of an alternative, and introduced money into this world. As the civilizations have developed and the needs of humans have increased, there was an increased need for a commonly agreed exchange medium.
During 700 BC, metal objects were introduced as money in Ancient India, along with the Chinese wen and Lydian staters. Metal was taken as a medium of exchange as it was available in abundance and easily stored and recyclable. Towards 10th century AD paper money got introduced, initially by China. In the modern world, every country has its own system of currency and coins.