What is an XMLHttpRequest object in AJAX?
The XMLHttpRequest (XHR) object is the key to AJAX. It is heavily used in AJAX programming to interact with servers. XMLHttpRequest can be used to retrieve any type of data, not just XML. It is supported by all modern browsers. It can be considered as an API that can be used by JavaScript, VBScript, and other web scripting languages to transfer and manipulate data to and from a server using HTTP.