A smart card is a credit card-sized card that contains an embedded microchip which allows it to store and process data. The microchip provides security features like authentication, data encryption, and secure communications. There are two main types - contact smart cards which require insertion into a reader, and contactless smart cards which communicate via radio frequency. Smart card readers allow communication between smart cards and other devices, and each manufacturer uses a different protocol. The microprocessor on smart cards enforces security by controlling access to stored data.