'AJAX (Asynchronous JavaScript and XML)' represents a group of web development techniques that utilize various client-side web technologies to create asynchronous web applications. AJAX enables web applications to transmit and receive data from a server in the background, asynchronously, without affecting the display or behavior of the current page.

First brought to widespread attention by Jesse James Garrett in 2005, AJAX represented a major advancement in web application technology. It uses the XMLHttpRequest object for server communication, allowing for asynchronous updates of web pages by exchanging small data quantities with the server discreetly. This approach facilitates updating sections of a webpage without needing to reload the entire page.

Rather than being a singular technology, AJAX is a combination of several technologies. It employs HTML and CSS for marking up and styling content, while JavaScript and the Document Object Model (DOM) are used to dynamically display content and interact with the user. The asynchronous data exchange with the server is achieved using JavaScript and XMLHttpRequest.

AJAX significantly enhances user experience by making interactions smoother and more responsive. It is extensively utilized in various web application functions such as form submissions, search suggestions, and updating content without reloading the entire page.

To conclude, the capacity of AJAX to fetch data asynchronously without the need for full page refreshes has revolutionized modern web application design, leading to faster, more dynamic, and user-friendly web experiences.