AngularJS is an open-source JavaScript framework for building dynamic web applications. It uses HTML as the template language and allows extending HTML vocabulary for the application. The key concepts covered in the document include modules and dependency injection, data binding using controllers and scopes, services, filters, form validation, directives, and routing. Various AngularJS features like modules, controllers, services, directives etc. are demonstrated via code examples. The document provides an introduction to core AngularJS concepts through explanations, code samples and a demo.