Core Android Concepts

 What is Android ?

Android is a software stack for mobile devices that includes an operating system, middle ware and
 key applications. The android SDK provides the tools and APIs necessary to begin developing
applications on the Android platform using the java programming language.

 Android Architecture

click here: http://premandroid.blogspot.in/2015/10/android-architecture.html

 Activity Life cycle

click here: http://premandroid.blogspot.in/2015/10/activity-lifecycle-in-android.html