Visa Debit lets you make online purchases with money taken directly from your bank account through the Visa network (Visa Canada). You use the card number at an online checkout much as you would a credit card, but you are spending your own funds rather than borrowing.
iGaming Ontario says operators generally accept debit or credit cards, though the exact list varies by operator (iGO FAQs). To deposit, you enter the card in the casino cashier and approve the payment, sometimes with an extra security check from your bank. Whether you can withdraw back to the same card depends on the casino and your card issuer, so read the cashier's withdrawal options before you deposit.
Debit cards suit players who want spending tied to money they actually have. The main catch is that your bank decides whether gambling transactions are allowed and whether they carry any fee. iGO recommends contacting your bank first because every institution has different rules on igaming payments. Casino minimums and maximums are set by each operator and shown in its cashier.
Source: www.visa.ca