What is needed to get started with Android?

1- What is Android?

Android is a operating system on mobile phones (and now it is also used on HD player, TV), developed by Google and based on the Linux platform. Previously, Android was developed by Adroid  Company (thereafter Google acquired in 2005).

The developers write applications for Android based on Java language. The launch of Android on November 5th, 2007 associated with the establishment of  handset open source alliances,  including 78 companies of hardware, software and telecommunications aimed at creating an open standard for mobile phones in the future.

2- Knowledge Required

Android was written based on Java language. To program Android applications, you need to know about Java and have basic knowledge about it.
You can start with Java at:

3- Android Development Tools

Before 2015, you need to install Eclipse  (A programming tool for Java) to program Android applications, then you need to install  plugin  into Eclipse, which allows you to program Android applications on Eclipse.
In 2015, Google launched the Android Studio, a programming tool for Android apps, and officially no longer supported Plugin for Eclipse.

Logically, the tools that are created for a specific task is always better. It means that you should select  Android Studio to program Android
On codewr.org website, we will provide you with the  Android programming instructions which is used  Android Studio tools. 
To install Android Studio.  you can see the instructions at: