Please tell me about android and how will I start developing android app.
Android is a mobile operating system developed by Google, based on a modified version of the Linux kernel and other open source software and designed primarily for touchscreen mobile devices such as smartphones and tablets.
If you want to make carrer in Android app developement start learning about android and android studio..
Android studio is the best software for develope android applications, which is open source and freely available.
Download Android studio from this link https://developer.android.com/studio/