AJAX is primarily JS interacting with a XMLHttpRequest:

Particularly, retrieval of data from XHR for the purpose of continually modifying a loaded web page is the underlying concept of Ajax design. Despite the name, XHR can be used with protocols other than HTTP and data can be in the form of not only XML, but also JSON, HTML or plain text

This is mostly off topic here, maybe try to get informed and reiterate your question.

I perhaps incorrectly called "AJAX layer" methods of the CMS, Perl methods that will be written to be called using AJAX in the browser or the HTML5 android app. But anyway, the concept is that the mobile app will be using the CMS as a data store, so methods for the life-cycle of any object need to be exposed by the CMS to the browser or calling app.