XMLHTTP Requests help us access JSON data.
AJAX allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes. They do this with a combination of XMLHTTPRequest objetcs and Javascript.
This can be helpful, for example, to create a menu. In this example we can see how we can access a list of links (which could be modified to create a menu):
XMLHTTPRequests can also be used to access header information (in this case for the txt file used in the example above), as in this example: