SSL, or Secure Sockets Layer, is a widely-used protocol for establishing secure, encrypted communication between two networked devices, such as a web server and a web browser. SSL uses a combination of public key and symmetric key cryptography to encrypt the data that is transmitted between the two devices, and to authenticate the identity of the devices. SSL is often used to protect sensitive information, such as login credentials, credit card numbers, and other personal or financial data, when it is transmitted over the internet. SSL is typically used in conjunction with the HTTPS protocol, which is a secure variant of the HTTP protocol that is used for transmitting data on the web. SSL is commonly used by websites, servers, and other networked devices to provide secure communication and protect the privacy of their users.