Ajax

A set of web development techniques that uses various web technologies on the client side to create asynchronous web applications. With Ajax, web applications can send and retrieve data from a server asynchronously (in the background) without interfering with the display and behavior of the existing page. By decoupling the data interchange layer from the presentation layer, Ajax allows web pagesWeb PagesHTML documents accessed via the internet.
More About Web Pages and, by extension, web applications to change content dynamically without the need to reload the entire page. In practice, modern implementations commonly utilize JSONJSONJavaScript Object Notation is a text-based format that represents data as key-value pairs.
More About JSON instead of XML.

Ajax is not a technology but rather a programming concept. HTMLHTMLThe fundamental language used to create and structure content on web pages.
More About HTML and CSSCSSCascading Style Sheets is a coding language that determines the appearance and layout of a website.
More About CSS can be combined to mark up and style information. The webpage can be modified by JavaScriptJavascriptA high-level, dynamic, and interpreted programming language primarily used to create interactive and responsive user interfaces on web pages.
More About Javascript to dynamically display—and allow the user to interact with the new information. The built-in XMLHttpRequest object is used to execute Ajax on web pages, allowing websites to load content onto the screen without refreshing the page. Ajax is not a new technology, nor is it a new language. Instead, it is existing technologies used in a new way.