A national bank is a financial institution that is chartered by the government of a country, region, or city. In the United States, national banks are chartered and regulated by the United States Treasury under the National Bank Act of 1863. National banks in the U.S. must have a Federal Reserve Identification Number, or FRN, and are designated with the initials NB.

National banks are commercial banks that provide all sorts of banking products and services, including savings accounts, checking accounts, consumer loans, mortgages, and more. They can also handle international transactions for their customers. National banks also play a role in the payment system by allowing customers to use their services, such as checks and electronic transfers, to send and receive payments.

Internationally, national banks are called "central banks" and are government-controlled. Central banks around the world have various responsibilities, such as supervising the country's financial system and setting economic policy. They are also responsible for creating and managing their country's money supply by issuing currency and monetary instruments such as coins, banknotes, and reserves. Central banks also influence the money supply by changing interest rates and apply other financial tools to support their country's economy.

National banking networks are also linked through the Federal Reserve. Banks that hold accounts with the Federal Reserve can access the Federal Reserve banking system for payments, deposits, currency and securities transactions. National banks use their affiliation with the Federal Reserve to facilitate and streamline their customers' transactions.

Regardless of whether the bank is international or domestic, national Banks provide a variety of services to individuals and businesses. Customers of national banks benefit from their services such as providing loans for purchases and investments, eliminating the need for outside financial institutions. National banks also act as a secure business conduit for transactions as customers are offered protection against fraud.

Overall, national banks provide customers with safety and convenience when it comes to their finances, as well as a platform for handling global transactions. They are highly regulated institutions, thus providing stability and trust in the country’s financial systems.