As stated previously, Ajax stands for Asynchronous JavaScript And XML.


Q : But what exactly does that mean?

Doing things Synchrously in Java Script

var data = database.query("SELECT Id FROM Employee");
console.log(data);
console.log("this is synchrous java script");

Doing things Asynchrously in java script

database.query("SELECT Id FROM Employee", function(data) {
    console.log(data);
});
console.log("this is asynchorous java script");

In First Case program will wait for the function database.query() to complete and then go to next line. But in the next case program will not wait for the function and will print the message in console before the query has been completed.

the result of above will be

I case:
all the Id's
this is synchrous java script

II case:
this is asynchrous java script
all the Id's 	

When we request a page we do it synchrously i.e. we have to wait for the response to proceed to the next step. But with it AJAX it is simple, communicate with the server and handle the response whenever request is completed in the mean time you can do your work.


Q : Where are Ajax used ?

• Search Suggestions
• Facebook uses it a Lot in chating, Like, Comment, etc.
• Real time Form Validation
• Login

Some resources to learn AJAX

Tutorials-Point AJAX
Creating Web Page with Asynchrous Java Script