Components

Every Angular App made of 1 or more components
Allows to work on smaller and more maintainable pieces that can be reused
Encapsulates Data, Html Markup/Template, Logic for View (area which user sees)
Every App has atleast 1 component called the AppComponent or Root Component
Angular embraces component based architecture which allows to work on small and more maintainable piece that can also be re-used
A real world angular app is a tree of component starting from AppComponent or the root component

Eg Components

Angular