It is not a technology but group of inter-related technologies. it includes following technologies
1. JavaScript
It is used to bring above technologies together. It used for Client-side validation and validate user input in an HTML form before sending the data to a server.
2. HTML/XHTML and CSS:-
These technologies are used for displaying content and style. It is mainly used for presentation
3. DOM:
It is used for dynamic display and interaction with data
4. XML/JSON:
For carrying data to and from server. JSON (Javascript Object Notation) is like XML but short and faster than XML
5. XMLHttpRequest
For asynchronous communication between client and server.