Casino deposit matches will convert your deposited cash into Casino Bonus and then award you an additional Bonus on top of that.
For example, if you opt into a 100% deposit match and then deposit $100, your $100 is converted into Casino Bonus and you'll receive an additional $100 in Casino Bonus. Since your deposited cash is now Casino Bonus, it can no longer be withdrawn or used for Sports betting until the Bonus play-through requirements are met or until you decide to abandon the promotion.