What is the Kraken 72 hour rule?

Could you please explain the Kraken 72-hour rule to me? I've heard it mentioned in a few discussions about cryptocurrency trading, but I'm not entirely sure what it means or how it works. Is it a safety measure? Does it apply to all transactions on the Kraken platform? And what happens if someone tries to withdraw funds within the 72-hour period? Your insights would be greatly appreciated.