No need to explain what a deposit is, but most, if not all casinos require at least X confirmations from the network in order to credit the deposit... but I'd like to know if there is an alternative to it.
Some crypto businesses do accept zero-confirmation transactions. But they take some precautions to make sure you won't be able to cancel the transaction and even if you do, it won't cause them any financial damage. In case of casinos, for example, they will instantly credit your account only when the transaction is non-RBF. But as this doesn't completely guarantee that the transaction can't be replaced, they will let you place bets but will lock withdrawals till the transaction gets enough confirmations.