Credit cards are thin plastic cards that authorize individuals to make purchases up to an established credit limit, using systems that verify account validity. The document highlights the evolution of credit card technology, particularly focusing on the 'blink' card, which utilizes RFID for faster, contactless transactions while maintaining security through encrypted data transmission. It also discusses the benefits and demerits of credit cards, emphasizing improved payment speeds and the need for additional security measures in the context of potential fraud.