Google Play allows many apps to have the same title. However, the application package for each app needs to be unique within Google Play. This is the package attribute value that you provide for the <manifest> tag in the AndroidManifest.xml file of your project. From the docs:
The package name serves as a unique identifier for the application.
which then continues:
Caution: Once you publish your application, you cannot change the package name. The package name defines your application's identity, so if you change it, then it is considered to be a different application and users of the previous version cannot update to the new version.
