The full form of AJAX is Asynchronous JavaScript and XML. It means AJAX makes use of the collaboration of Javascript and XML in order to allow the web pages to remain in an updated version with a new data from the server. AJAX is equipped with HTML, JavaScript, DHTML, and DOM.

One of the most common ways of processing data between the browser of the client and a server was to submit a HTML form and then it is due to send the date to the server, the server processed the data and then send a response back to the browser.

There are a lot of pros and cons of this method but the most disadvantageous thing about this method is that the web page must be reloaded in the browser.

AJAX follows an all together different approach and allows to write web-applications without even having the need of reloading the page again when a user interacts the next time. So it becomes easier for us to create better, faster and easier to use web applications.

To learn AJAX, one must have a basic information and knowledge about HTML as well as Javascript. But if you don't have any kind of knowledge, that means if you are a beginner, then there is no need to worry as there are short courses that are available for the beginners.

One must always keep this thing in mind that in order to create or work on a AJAX page, one must have a server to run it. You can also have a local host on your computer, or even a remote server that should be managed by a web hosting company.

AJAX makes use of uses JavaScript language through HTTP protocol. This is done in order to exchange the data.
If somehow, you tend to go to Yahoo Finance or Google Finance, then you will be able to note that the stock quotes on their pages have the tendency to change automatically. There is no need to refresh the page over and over again.
We can use AJAX to update data dynamically without even having the need to upload the page.