Web Sockets in HTML 5
HTML5 WebSockets, defines a full-duplex communication channel that operates through a single socket over the web. WebSocket is not just another incremental enhancement to conventional HTTP communications, it represents a large advance, especially for real-time, event driven web applications.
Normally when a browser visits a web page, an HTTP request is sent to the web server that hosts that page. The web server acknowledges this request and sends back the response.