Confession : I don't think I'm ever going to really understand money laundering, no matter how many TV shows explain it.

For a good reason: they make it as complex as possible so it won't be easily discovered. But in its simplest form: they make hard-to-trace transactions (often in cash: tips, street artists, produce stalls, hot dog stands, small shops, etc.) so they can easily "import" money made through illegal means.

Spendings are masked by easily "lost" inventory. Like, a grocery store that declares their orange order came in all rotten.

Money is moved through bogus corporations several time and comes
back as legit funds.

How does money laundering work? - Delena D. Spann

it's where you leave your cash in your pocket, then wash your trousers, isn't it? (UK money will now survive this operation!)