Android Studio is a version of JetBrain's IntelliJ Community Edition specifically tailored for Android development. Installation instructions for IntelliJ IDEA can be found here.
IntelliJ IDEA contains all the features found in Android Studio. Setup for Android development is, however, a bit more involved since it does not include the Android SDK by default.
- Install Java JDK
- Install IntelliJ IDEA
- Install Android SDK Tools
- Install Genymotion