Getting cash from Credit Card is expensive. There are multiple type of charges depending on the Bank;
- A fixed Transaction / cash Advance Charge.
- A percentage fee on the amount of withdrawl.
- Interest from the day of withdrawl till the date of payment. [Unlike purchases, there is no grace period for payments]
Getting cash from Debit card is no charge.
Cash Back is the loyalty bonus when you purchase from some stores [can even be wider] essentially involves passing back some of the fees Bank would make back to the customer.
On every card swipe of say 100, the merchant gets only 97.5, the rest 2.5 goes as fees, of which the merchant Bank [where the POS/Gateway is connected] gets 0.5, Card Company [Visa/Master/Amex/etc] get 0.5, the Issuing Bank [the one that gave you credit card] gets 1.5. The reason they get large amount is because they give you a average credit of 30 days [at times 10 days at times 50 days depending on when the transaction was done] ...
If the same bank as POS, then on the transaction the Bank makes both legs of fees, ie 2. It is from this fee, they can pass back a small amount say 1 to you.
Again the above is slightly simplified, the fees and distribution varies from Visa to master and from one Merchant Bank to Other, the Cash Back itself is conditional [tied to places where it has POS] or unconditional for limited period to get more customers, or built with other spedning incentives [ie spend minimum of X amount to get cash bank], essentially encouraging spending and not all may be rewarded, or a cap on the total cash back given.