The
android tool provides you with commands to create all three types of
projects. An Android project contains all of the files and resources that are needed to build a
project into an .apk file for installation.
- An Android project contains all of the files and resources that are needed to build a project into an .apk file for installation. You need to create an Android project for any application that you want to eventually install on a device.
- You can also designate an Android project as a library project, which allows it to be shared with other projects that depend on it. Once an Android project is designated as a library project, it cannot be installed onto a device.
- Test projects extend JUnit test functionality to include Android specific functionality. For more information on creating a test project, see Testing from other IDEs.
http://developer.android.com/tools/projects/projects-cmdline.html