Link:
So basically this method shows you how you can doublespend transaction that have 1 confirmation in the blockchain (basically the transaction will disappear from the blockchain and funds will be back to your wallet like you never made that transaction). Some casinos and sportsbook sites (and even online stores) release the funds / products after your transaction get 1 confirmation - then you can use this method to get your money back and keep the product.
This is obviously unethical, but that is purely the sites mistake that they don't wait for at least 3 confirmations. If you wanna try this yourself, you can read this method here: