Let's hear from Jeanne Gobat, Senior Economist in the IMF's Monetary and Capital Markets Department, writing in 2012 on Banks: At the Heart of the Matter:

Although banks do many things, their primary role is to take in funds -- called deposits -- from those with money, pool them, and lend them to those who need funds. Banks are intermediaries between depositors (who lend money to the bank) and borrowers (to whom the bank lends money).