The activity of finances is the application of a whole of techniques that the individuals and the organizations (entities) employ to control their financial businesses, in particular the differences between the income and the expenditure and the risks of their investments. An entity whose income exceeds its expenditure can lend or invests the excessive income. In addition, an entity whose income is lower its expenditure can join together the loan capital or by selling complaints of stockholders' equity, decreasing its expenditure, or increasing its income.

The lender can find a borrower, a financial intermediary, such as a bank or notes or bonds of purchase on the bond market of the obligations. The lender arouses the interest, the borrower pays an interest higher than the lender receives, and the financial intermediate pockets the difference. A bank incorporates the activities of many borrowers and lenders. A bank accepts deposits of the lenders, on whom it pays the interest. The bank then lends these deposits to the borrowers. The banks allow borrowers and lenders of various sizes to coordinate their activity. The banks are thus compensators of the money flows in space since they allow various lenders and loans to meet, and in time, since each borrower will pay thereafter behind.

Finances of the individuals, the businesses, and the states: Finances are employed by Individuals (personal finances), by governments (finance public), by the companies (finances of corporation, etc...) as well as close a large variety of organizations including/understanding of the schools and the non-profit organizations. In general, the goals of each activity above are achieved by the use of the adapted instruments, with the consideration with their institutional arrangement.