Today's Web Apps are not that Simple, they should offer more-native-app-like experience to the user. The Web Application should not reload the whole page whenever a user request something. First we have to familiar ourself with the concept of Single page application.
Now, how angularJS fits itself into Single Page Application concept.
HTML was not designed for dynamic views, but it is great for declaring static documents. Angular helps to extend HTML and gives behaviour to HTML which helps in declaring dynamic views in web-applications.
In my Future posts I will discuss the features of angular like directives, Controllers, Models, Routes, Factories, services etc. The following picture helps to understand the power of angular.