An Automated Teller Machine, or ATM, is a machine that allows customers to complete basic transactions without the aid of a branch representative or teller. Customers can use an ATM to access cash (or any other type of account), as well as make deposits and withdrawals. Anyone with a credit card or debit card can access cash at most ATMs.An ATM works by inserting money into a slot at the front of the machine, which prompts it to dispense cash. The customer then gets his or her deposit slip and leaves with it. The whole process takes less than a minute, and there's no need for paper statements or waiting in line.