Imagine you officially don't have a job, yet you deposit a certain amount of money to your account every week, or you buy a fancy new car every 2 months. Something's fishy about it. How do you obtain the money? Are you paying taxes on it? Internal Revenue Service (IRS) won't be happy if you are not...

So, how do you launder the money? Saul Goodman did a great job explaining that in Breaking Bad to a 5-years old Jesse Pinkman (see link below). You open a car washing business. Let's pretend an imaginary person (Mr. Invisible) comes to your business to wash his car, total is 30$. He pays for it with your "dirty" money which you are hiding somewhere. You register the transaction and issue a receipt of payment. These 30$ are now clean and you can deposit it in your bank account. You are gonna pay taxes on it, so it won't be 30$ after taxes but a lower amount, you lose a bit of money in the process. Nevertheless, now it's clean money, you have a valid reason (and a proof) for having such money on your account, which is the issued receipt and the registered transaction.

https://www.youtube.com/watch?v=ez6xH-su2xI&ab_channel=VincenzoCortino