Societies invented currency to facilitate economic activity.
Currency means that a person can sell something without having to receive a specific good in exchange.
Currency and payment systems allow people to travel to distant places for long periods and enable companies to do business with other companies operating in faraway locations.
Currency also means that the surplus resources (savings) of economic agents – individuals, households and companies - can be channelled to others who need them (investment). This operation not only enables people investing their resources to earn income in the future but also increases investment and entrepreneurship.
The financial system and the banks in it play a crucial role in the economy's use of currency.
Banks run the payment systems that enable local markets to operate and individuals and companies to travel to distant places and act there. Without a well-structured banking system, currency would not be able to circulate and it would also be harder to create markets for goods and services and for people and goods to circulate.
Banks are also essential as financial intermediaries. In other words, they take the savings of people with surplus resources and make them available to others who need them. Without this operation, people's and companies' ability to invest would be very limited.