WebSockets is a web technology, part of HTML-5 specification, that provides certain bi-directional (full-duplex) communication channels between a web-client and a web-server, using a single TCP connection.
Lately the related WebSockets API is being standardized by W3C, while the WebSocket protocol has been standardized by the IETF on the RFC-6455.
The actual new feature –considering user-experience– that is introduced with WebSockets is a sense of live bi-directional streaming experience.
A very good example of WebSockets technology is GILT Live, a URL that shows the on-line purchases currently happening on the well-known e-shop of GILT Groupe!
NOTE: have you noted the [Pause] button?
Note also that WebSocket protocol is currently supported in several browsers including Firefox, Safari and Google Chrome.