As the title suggests, ATM and credit card scams are based on the delivery of a supposed physical ATM or credit card, which is preloaded with a large sum of money. Delivery can often involve a fake bank, government agency, delivery company, courier, diplomat, bank officer, delivery agent, etc. Claims usually involve an ATM card which is waiting to be delivered or failed to be delivered and with the source of the funds contained in the card will be often be stated as coming from many different sources.
In all cases though these scams involve a type of fraudulent criminal practice known as “Advance Fee Fraud”, a.k.a. “419 Scams”. If you are not yet familiar with these two terms then the following article on Wikipedia can help you to understand more about how most of these types of scams operate: Wikipedia Link