Reason of why use Ajax
There are 3 reason of using Ajax in web applications:
Callbacks: Ajax is used to perform a callback, making a fast round trip to and from the server to retrieve and/or save data without posting the entire page back to the server. Without performing postback and send all form data to the server.
Making Asynchronous Calls: Ajax allows you to make asynchronous call to the web server/database. The Ajax allows the client browser to avoid waiting for all data to arrive before allowing the user to act once more.
Increased application Speed: The main reason of Ajax is to improve the speed and performance of a web application. For example: The user rates a blog and their personal rating for that blog will be saved to their database without waiting for the page to refresh or reload. These blog ratings are being saved to their database without posting the entire page back to the server.