A bank is a commercial or state institution that provides financial services, including issuing money in form of coins, banknotes or debit cards, receiving deposits of money, lending money and processing transactions. A commercial bank accepts deposits from customers and in turn makes loans based on those deposits. Some banks (called Banks of issue) issue banknotes as legal tender. Many banks offer ancillary financial services to make additional profit; for example: selling insurance products, investment products or stock broking.

Currently in most jurisdictions commercial banks are regulated and require permission to operate. Operational authority is granted by bank regulatory authorities and provide rights to conduct the most fundamental banking services such as accepting deposits and making loans. A commercial bank is usually defined as an institution that both accepts deposits and makes loans; there are also financial institutions that provide selected banking services without meeting the legal definition of a bank.

Banks have a long history, and have influenced economies and politics for centuries. In history, the primary purpose of a bank was to provide liquidity to trading companies. Banks advanced funds to allow businesses to purchase inventory, and collected those funds back with interest when the goods were sold. For centuries, the banking industry only dealt with businesses, not consumers. Commercial lending today is a very intense activity, with banks carefully analyzing the financial condition of its business clients to determine the level of risk in each loan transaction. Banking services have expanded to include services directed at individuals and risk in these much smaller transactions are pooled.

A bank generates a profit from the differential between what level of interest it pays for deposits and other sources of funds, and what level of interest it charges in its lending activities. This difference is referred to as the spread between the cost of funds and the loan interest rate. Historically, profitability from lending activities has been cyclic and dependent on the needs and strengths of loan customers. In recent history, investors have demanded a more stable revenue stream and banks have therefore placed more emphasis on transaction fees, primarily loan fees but also including service charges on array of deposit activities and ancillary services (international banking, foreign exchange, insurance, investments, wire transfers, etc.). However, lending activities still provide the bulk of a commercial bank's income.

The name bank derives from the Italian word banco, desk, used during the Renaissance by Florentines bankers, who used to make their transactions above a desk covered by a green tablecloth. -Wikipedia.org