I want to submit search query form & get search result without redirecting/reloading/refreshing on the same pa
You'll probably want to start with any of the thousands of "AJAX for beginners" tutorials you can find on the net. A Google search with that term should get you going.
Try this for starters:
http://www.destraynor.com/serendipity/index.php?/archives/29-AJAX-for-the-beginner.html
After you've read through that, keep in mind that you really don't need to be writing any XHR handling code. As pointed out by Jamie, jQuery or any of the other multitudes of Javascript libraries out there, can greatly simplify your client-side AJAX code.