from source code and assets to test code and build configurations.
Additional modules are useful when creating code libraries within your own project or when you want to create different sets of code and resources for different device types, such as phones and wearables, but keep all the files scoped within the same project and share some code.
Android app module: 默认模组
Feature module: 额外功能（优化应用商店管理）
Library module: 类库，不提供安装；需要提供依赖
Provides a container for your reusable code, which you can use as a dependency in other app modules or import into other projects. Structurally, a library module is the same as an app module, but when built, it creates a code archive file instead of an APK, so it can't be installed on a device.
In the Create New Module window, Android Studio offers the following types of library modules:
- Android Library: Contains all file types supported in an Android project except native C++ code, including Java and Kotlin source code, resources, and manifest files. The build result is an Android Archive (AAR) file that you can add as a dependency for your Android app modules.
- Android Native Library: Contains all file types supported in an Android project, similar to an Android Library. However, Android Native Libraries also can contain native C++ source code. The build result is an Android Archive (AAR) file that you can add as a dependency for your Android app modules.
- Java or Kotlin Library: Contains only Kotlin or Java source files. The build result is a Java Archive (JAR) file that you can add as a dependency for your Android app modules or otherKotlin or Java projects.