HTTP/1.1 is a version of the Hypertext Transfer Protocol, which is the foundation of data communication on the World Wide Web. Introduced in 1999, it improved upon its predecessor, HTTP/1.0, by adding features like persistent connections, allowing multiple requests and responses to be sent over a single connection, which enhances performance. Additionally, HTTP/1.1 introduced chunked transfer encoding, enabling the server to send data in segments, and better caching mechanisms to reduce server load and improve response times. These enhancements made web browsing faster and more efficient, contributing to the growth of the internet.