SSL (Secure Sockets Layer) and TLS (Transport Layer Security) are protocols for establishing secure communication links between computers in a network. They are used to encrypt data transmitted between two devices to protect it from being intercepted by third parties. SSL and TLS are commonly used to secure communication over the Internet, such as when a web browser communicates with a web server to request and display a webpage. They are also used to secure other types of network communication, such as email and file transfers.