A key card is a small, plastic card that uses a magnetic stripe or embedded chip to grant access to secure areas, such as hotel rooms or office buildings. Users simply swipe or tap the card on a reader to unlock doors, making it a convenient alternative to traditional keys. Key cards are often part of a larger security system that may include key card readers, access control software, and security protocols. They can be programmed to allow access only to specific individuals or during certain times, enhancing security and tracking who enters restricted areas.