Android is an open-source mobile operating system based on a modified version of the Linux kernel and other open source software, designed primarily for touchscreen mobile devices such as smartphones and tablets.

Android also is a Smart TV operating system.

Android Development Guide

Install Android Development Studio

http://www1.alx.pl/w/android/android101

http://www1.alx.pl/w/android/android201

https://www.android.com/