AngularJS is a free, open-source JavaScript framework developed by Google for building dynamic, single-page web applications (SPAs). It extends HTML with features like two-way data binding, directives, and reusable components, following a Model-View-Controller (MVC) architecture. AngularJS helps create responsive, interactive web apps by separating concerns, simplifying code maintenance, and supporting real-time updates. While it offers many benefits like fast prototyping and cross-browser compatibility, it requires server-side security and won’t work if JavaScript is disabled in the browser.