The transition of technology with time, culminating into the evolution of AJAX can be discussed as follows.

During the initial days of browser innovation, Netscape added a feature known as "LiveScript" that permitted the software developers to embed small scripts in web pages so that they can continue doing things even after these are downloaded.

LiveScript became JavaScript, a more powerful scripting tool. This again led to a new technology called as Dynamic HTML (DHTML).  DHTML allowed making things soar around the screen and get changed in response to user inputs. DHTML implementations did not have much weight and was cumbersome too.

Netscape presented another new technique called Dynamic XML just before the time when web application development almost died out. Within this period Microsoft had made available a function called "XMLHttpRequest" to Internet Explorer version 5. This was followed by Mozilla and this function stayed unused for a long time awaiting the development world to take its best advantage and usability. 

XMLHttpRequest permitted the JavaScript embedded within the web pages to fetch more data. This was something new as prior to this, getting more data would require another web page to be sent. The JavaScript within a web page was unable to talk to the external world. This has been changed by XMLHttpRequest as it is permitted to fetch more data from server as and when required.

This new technique was named AJAX (acronym for “Asynchronous JavaScript and XML”) by Jesse James Garrett of “Adaptive Path” during February 2005. The technique became popular within a very short time. JavaScript toolkit became more effective in making this development easier. And thereafter, AJAX became a buzzword in the web application development.