Earlier Eclipse was the only famous development platform for Android applications. Later in 2013 Google introduced Android Studio. During the initial stage it had few issues but Google have fixed them and now it is a nice Android development tool to work with.
As the Official Android development IDE is ready from Google itself, Google announced that they will be stopping the official support for Eclipse by the end of this year. This will include ADT plug-in for eclipse and also the Android Ant build system.
Here is a part of the official announcement
Over the past few years, our team has focused on improving the development experience for building Android apps with Android Studio. Since the launch of Android Studio, we have been impressed with the excitement and positive feedback. As the official Android IDE, Android Studio gives you access to a powerful and comprehensive suite of tools to evolve your app across Android platforms, whether it's on the phone, wrist, car or TV.
To that end and to focus all of our efforts on making Android Studio better and faster, we are ending development and official support for the Android Developer Tools (ADT) in Eclipse at the end of the year. This specifically includes the Eclipse ADT plugin and Android Ant build system.
If you are a developer who uses the Eclipse to develop apps, you can migrate your projects easily using the Import project on the Android Studio.
Read more here