A money order is a special piece of paper you can buy that works like a guaranteed check. When you purchase a money order, you pay the full amount upfront (plus a small fee), and the company that sells it prints that exact amount on the paper. The person who receives it can then cash it or deposit it like a check, but unlike a regular check, the money is already paid for and guaranteed.

Money orders became popular in the 1800s as a safe way to send money through the mail. If you mail cash and it gets lost or stolen, it's gone forever. If you mail a money order and it gets lost, you can often get your money back. Plus, the recipient knows the money is real: no one can write a bad money order the way someone might write a check when they don't actually have money in their bank account.

Today, people still use money orders when they need to pay someone but don't have a checking account, or when the person they're paying doesn't trust personal checks. You can buy money orders at post offices, banks, and many grocery stores. Some landlords require tenants to pay rent with money orders because they're more reliable than personal checks. The money order includes spaces where you write who should receive the money and who it's from, making it official and easier to track.