ATM stands for Automated Teller Machine, a computerized banking terminal that lets people access their money without going inside a bank or talking to a human teller. You've probably seen these boxy machines outside grocery stores, gas stations, or bank branches, with screens and keypads where people insert plastic cards.

When you have a bank account, the bank gives you a debit card with a magnetic strip or chip. At an ATM, you insert this card and type in a secret PIN (personal identification number) to prove you're really you. Then you can withdraw cash, check your account balance, or deposit money, all handled by the machine's computer system connected to your bank's network.

ATMs revolutionized banking when they became common in the 1970s and 1980s. Before ATMs, if you needed cash on a Saturday afternoon or after 5 p.m., you were out of luck because banks were closed. Now people can access their money 24 hours a day, seven days a week.

The phrase “like an ATM” means treating someone or something as an endless source of money. If someone complains that their parents aren't “an ATM,” they mean their parents won't just hand over cash whenever asked.