You don't hold the money in your bank. Your bank does.
When your balance sits with a bank or an exchange, you own a claim on an institution, and you trust it to honour that claim. Usually it does, but sometimes it doesn't.
Self-custody is the other option. You hold your money directly, and nobody else can move or freeze it.
For years it had a hard catch: the seed phrase. One lost piece of paper, and the money was gone for good.
That has changed.
Self-custody now works without a seed phrase. A passkey on your device takes the place of the twelve words, so there's nothing to write down and nothing for a scammer to talk out of you.