HTTPS (HyperText Transfer Protocol Secure) is an extension of HTTP for secure communication over a computer network. HTTPS uses encryption protocols such as SSL (Secure Sockets Layer) or TLS (Transport Layer Security) to encrypt data transmitted between the client and server, ensuring the confidentiality and integrity of the data. It provides authentication of the website and protects against man-in-the-middle attacks, eavesdropping, and tampering. HTTPS is crucial for secure online transactions, protecting sensitive information such as login credentials, personal data, and payment details.