HTTPS, or HyperText Transfer Protocol Secure, is an extension of HTTP used for secure communication over the internet. It encrypts the data exchanged between a user's browser and a website, protecting it from being intercepted or tampered with by third parties. This encryption ensures that sensitive information, like login details or payment data, remains private and secure. HTTPS also helps build trust, as many browsers display a padlock icon to indicate that a website is secure, and search engines prioritize HTTPS sites in search results.