sending data to server and updating a page

I have been writing php scripts to send forms to the users browser. The user fills in the form and presses a submit button. The information is transmitted to the server and the server sends a new page to the browser. All pretty standard.

I have seen applications where the user fills in some fields on a web page and clicks a submit button. The information is transmitted back to the server which does some processing and sends some info back to the browser. The new information is displayed in the appropriate places on the users browser but the key thing is that the whole page is not re drawn. It is much faster.

I presume that there is some Java script running on the users browser that interacts with the script on the server.

Hows it done is basically the question.

http://www.modernmethod.com/sajax/