As suggested by the name, commercial banks do business with other businesses, from small family businesses to multi-national corporations. These include industrial banks, which focus on various types of industries, and stock savings banks, which specialize in building value for company stocks. Other types of commercial banks are national and state chartered banks and trust companies.
The purpose of these banks is similar to banks that serve the public. They offer interest on business savings and other investment opportunities and they offer loans. It is these business loans that grease the wheels of industry. It is the savings and investments that provide the capital for the loans. Many companies also have lines of credit with their institution, which allow them to use money as needed, up to a pre-set limit and pay it back as they are able.
Very few businesses, whether large or small, are able to operate on a cash and carry basis. Loans are frequently needed when business is slow and money is needed for inventory or payroll. Cyclical businesses especially need to be able to weather down times with business loans.
Billions of dollars change hands every day in the commercial banking business, most of it with a computer keystroke. Most businesses could not survive without a good return on their investments or without the occasional loan. It works out well for the business customer as well as the commercial bank.