SSL, or Secure Sockets Layer, is a technology that creates a secure connection between a web server and a browser. It encrypts the data exchanged between the two, ensuring that sensitive information, like passwords and credit card numbers, remains private and protected from eavesdroppers. When a website uses SSL, it displays a padlock icon in the browser's address bar, indicating that the connection is secure. This helps build trust with users, as they can be confident that their data is safe while browsing or making online transactions. SSL has largely been replaced by TLS (Transport Layer Security), which is a more secure version of the protocol.