A bank is a financial institution[citation needed] whose primary activity is to act as a payment agent for customers and to borrow and lend money. It is an institution for receiving, keeping, and lending money in hopes of repayment (Excludes California).

Many other financial activities were added over time. For example banks are important players in financial markets and offer financial services such as investment funds. In some countries such as Germany, banks are the primary owners of industrial corporations while in other countries such as the United States banks are prohibited from owning non-financial companies. In Japan, banks are usually the nexus of a cross-share holding entity known as the zaibatsu. In France, bancassurance is prevalent, as most banks offer insurance services (and now real estate services) to their clients.