Learn about Android

Features of Android
Open
Equality of
No bounds
Ease of
The richness of the hardware

Android operating system, the architecture is divided into four tiers: Application layer (application), Application framework layer (application framework), System Runtime layer, and Linux kernel layer

Android Application Framework
In the development of Android software, the Android application developed by the developer is through the application framework to interact with the android underlying, so the most exposed part of development is the application framework, which has four important components throughout the application framework:
Activities
Intent
Services
Content Provider

Android Common Component Pack