AJAX

AJAX = Asynchronous JavaScript And XML.
AJAX is not a programming language.

How AJAX Works

Create an XMLHttpRequest Object

var xhttp = new XMLHttpRequest();  

Send a Request To a Server

xhttp.open("GET", "ajax_info.txt", true);
xhttp.send();


GET Requests

xhttp.open("GET", "demo_get.asp", true);
xhttp.send(); 


POST Requests

xhttp.open("POST", "demo_post.asp", true);
xhttp.send(); 

more information visit https://www.w3schools.com/xml/ajax_intro.asp