'HTTP (Hypertext Transfer Protocol)' is the cornerstone of web data exchange, facilitating the transmission of hypermedia documents like HTML. It outlines the structure and transmission of messages, guiding web servers and browsers in their interactions.

HTTP operates as a client-server protocol with a request-response model. Browsers request data, and servers respond, typically with web content. HTTP's stateless nature, treating each request as new, ensures simplicity and speed, with technologies like cookies adding continuity for user experiences.

HTTP has advanced over time, with HTTP/2 and HTTP/3 enhancing security and efficiency, marking its continuous evolution in web communication.