What's the purpose of "Instant Dynamic Feature Module"

As the[ documentation](https://developer.android.com/guide/app-bundle/instant-delivery#dynamic_feature_manifest) says:

- **Additionally, when downloading and installing your app, instant-enabled dynamic features are automatically downloaded and installed with your app’s base APK**

- **"This behavior means that when you set dist:instant="true", you cannot also include ."**

Then if we can't deliver [dynamic feature] on demand with "Instant App",Why don't we just use the " android library module" instead of "Instant Dynamic Feature Module"?

Start with the linked Android App Bundle instant-delivery documentation and inspect the repository's Instant Dynamic Feature Module sample. The issue names no file or test, so first determine which sample documentation explains the module's purpose and how it differs from an Android library module. Done means adding a clear explanation supported by the sample's configuration.

Written by the indexing model from the issue text.