Banks can make new money when they lend. New loans throughout the banking system create new deposits elsewhere in the system. This money is usually raised by lending behavior and decreases as loans are repaid faster than new loans are made.
The major earning of the banks in interest. They give money to its customers on interest and receive more than its principal value. They also provide many other small services like bank transaction, government bonds, mutual bonds etc. they also invest their capital in different project and receive its shares. On the whole banks earn from many resources.