Is Ajax a technique for communication between client & server or is it contain more than that. i know that the technique is use for communication but can we do more than that using Ajax. i mean do Ajax has some other purpose as well?
I am quite new to ajax but love it already. We have surprised our customers with Ajax so far. A brief definition is:
A scripting technique for silently loading new data from the server. Although AJAX scripts commonly use the soon to be standardized XMLHttpRequest object, they could also use a hidden iframe or frame. An AJAX script is useless by itself. It also requires a DOM Scripting component to embed the received data in the document. domscripting.webstandards.org/
I think Diego gave an excellent definition of what AJAX is in simplest terms.
However, where I think things get intersting is when you realize that for most web developers, it represents a whole new way of looking at applications.
When you start to think about being able to refresh small portions of a page, or not update the display at all but do processing behind the scenes between the client and server, you start to realize that you can deliver applications that look, feel and most importantly *function* like fat-clients, you start to see the potential. The whole Rich Internet Application movemement comes about from this.
As many people, including myself, like to point out, AJAX is not new. The actual techniques are a few years old, but the basic underlying approach is even older... as I describe in my book, I did an application around the 2000 timeframe that worked in an "AJAX-like" fashion, but didn't use what we call AJAX today. But, it's true that many, perhaps even most, web developers learned to do things the "standard" way, so AJAX is in fact something new for them, and that's why it's getting so much attention.
I should also point out that AJAX has *nothing* to do with effects, animation, and that sort of thing. That's just good 'ole fashioned DOM scripting, or dHTML if you prefer (some people shun that term nowadays, but it's more or less the same basic thing). Many libraries out there today have AJAX functionality as well as animations and such, so they often get lumped together. It's really not accurate to do so though.