Banking in its modern sense evolved in the 14th century in the rich cities of Renaissance Italy but in many ways was a continuation of ideas and concepts of credit and lending that had its roots in the ancient world. A bank is a financial institution and a financial intermediary that accepts deposits and channels those deposits into lending activities, either directly by loaning or indirectly through capital markets. A bank is the connection between customers that have capital deficits and customers with capital surpluses.
Due to their influence within a financial system and the economy, banks are highly regulated in most countries. Most banks operate under a system known as fractional reserve banking where they hold only a small reserve of the funds deposited and lend out the rest for profit. They are generally subject to minimum capital requirements which are based on an international set of capital standards, known as the Basel Accords.
A bank can generate revenue in a variety of different ways including interest, transaction fees and financial advice. The main method is via charging interest on the capital it lends out to customers. The bank profits from the difference between the level of interest it pays for deposits and other sources of funds, and the level of interest it charges in its lending activities.