AJAX+ASP.NET

As far i learned ....AJAX is used for partial page refresh (overcoming the flickering effect in the web page) ....Is there any other features in AJAX....

Technically Yes. Ajax is used for "partial page" refresh there by eliminating the complete page refresh. There are 2 main advantages

1. Data transfer : Data transfer (To and from the server) is less compared to the entire page refresh
2. Better User experience : Since the user will not be seeing a blank page it gives the user an illusion of interacting with the site.

What can be done using AJAX is an ever ending list.

Ex: Gmail uses AJAX for it email. If you are using gmail and compare it with other email providers you will know the difference.

Facebook has rich AJAX features in its site.

SO uses AJAX for comments

I think What AJAX cannot do will be easier to mention. For example

AFAIK web browsers cannot maintain the view state of the AJAX enabled website.

Some AJAX enabled websites do not render properly in mobile browsers.

Anythign more?