A debit card transaction occurs when a customer uses their debit card to make a purchase or withdraw cash from an ATM. The amount spent is directly deducted from the customer's bank account, allowing for immediate access to funds without borrowing money. During a debit card transaction, the card is swiped or inserted into a payment terminal, and the customer may need to enter a PIN for security. This process ensures that only the account holder can authorize the transaction, providing a safe and convenient way to manage everyday expenses.