What is the primary function of a bank? Why do people prefer banks over other financial intermediaries?

The primary job of a bank is to act as an intermediary, taking in deposits from savers and loaning that money to people who want to borrow.

People deposit their money in banks for two main reasons. First, depositing money in a bank is much safer than stashing money in a jar or stuffing it under a mattress. Secondly, depositing money into checking accounts gives consumers easy access to it, either through checks or through cash cards. Deposits are guaranteed safe through deposit insurance, and it may even earn money in interest, depending on the type of deposit account.