Banks! - we cannot really live without them, and they are a large component of everyday life.
People earn money to meet their day to day expenses on food, clothing, education of children, and so on. They also need money to meet future expenses on marriage, higher education of children, housing, building, travel and social functions. 
These are heavy expenses, which can be met if some money is saved out of the present income. In the old days, and still with some people today, savings were stashed away in hiding places and were available for use whenever needed, but this involved the risk of loss by theft, robbery and other accidents.
Thus, people were in need of a place where money could be saved safely and would be available when required. Banks are such places where people can deposit their savings with the assurance that they will be able to with draw money from the deposits whenever required.
A Bank is a lawful organization which accepts deposits that can be withdrawn on demand. It also lends money to individuals and businesses that need it, provided they can satisfy the criteria imposed by the banks to minimize their risk of lending.