system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: I have a debit card, but every time I use it i'm asked "credit or debit", what's the difference and why do they ask me if it's specifically a debit card?
gpt
For the love of god, ignore the other answers. 


"Credit" and "debit" transactions are processed via different networks with different fees to the merchant. 


"Credit" transactions are processed using either the Visa or MasterCard network, just like credit cards. Merchants need to pay fees on these transactions, typically starting around $1. This is why many merchants have a minimum transaction amount. Unlike what other people posted here, signatures are not required, even for in-person purchases. A portion of the fee is actually paid to the issuing bank. 

"Debit" transactions are processed via the same network as ATM withdrawals. For this reason, you can generally use any ATM card at a merchant that allows debit purchases, as long as the card is attached to a checking account. These transactions require a PIN, just like ATM withdrawals and the fees to merchants are lower. Also, because it uses the ATM network, many merchants will allow you to get cash back on purchases. Issuing banks are not paid a portion of these fees, which is why some banks will charge a small fee, typically $0.25 to $0.50 when purchases are processed this way.