Ajax (Asynchronous JavaScript and XML) is a web development technique used to create interactive web applications. It is a combination of HTML, CSS, JavaScript, and XML that allows web pages to be updated asynchronously by exchanging data with a web server through the use of web services. The technique consists of a combination of web technologies that allow the web page to process user input and update content in the background without refreshing the page. This technology can be used to build applications that offer more responsiveness, speed, and user control. Ajax can be used in various technologies like HTML, CSS, JavaScript, XML, and other tools. The key components of Ajax are the XMLHttpRequest object and the JavaScript callback functions. The XMLHttpRequest object allows data to be exchanged from the web server without reloading the page. The callback functions enable the client to process the response coming from the server. By combining these two technologies, web developers are able to make web applications more responsive and user-friendly.