Cashier's Check

A personal check might bounce. A cashier's check...won't.

When you write a check out of your checking account (i.e. a personal check), you're basically making a promise that the money is there. The person receiving the check takes it to their bank, and then that bank contacts your bank, who then checks your account. If there's not enough money there, they'll let the first bank know that there are insufficient funds. The original bank will do the equivalent of a sad-face emoji to their client, and then charge them $20 for depositing a bounced check. You'll probably get a fee, too, plus an angry phone call from the person you wrote the check to.

For a cashier's check, the money comes out of your account at the moment the check is issued (or you give some cash to cover it to the cashier). The check isn't attached your your account...it's backed by the bank. If someone asks for a cashier's check, it means they don't want the risk that the check will bounce. For the person receiving it, it's much closer to cash in terms of the guarantee that they'll get the money.