Secure Sockets Layer (SSL) is a standard Protocol used for the secure transmission of documents over a network. Developed by Netscape, SSL technology creates a secure link between a Web Server and browser (i.e., Client to ensure private and integral data transmission. SSL uses Transmission Control Protocol (TCP) for communication.
See: RFC6101 - The Secure Sockets Layer (SSL) Protocol Version 3.0
Source: https://www.techopedia.com/definition/24025/secure-sockets-layer-ssl