These files are examples, samples, and goodies that are used in conjunction with the book "Android Development Patterns" available from Addison-Wesley Professional.
Note that many of these projects are not complete, instead they contain snippets that can be ported to your own project. Some of them are also for reference on file structure and layout.
You should also note that projects will need to be altered to match your envionrment. This means that you may need to set project paths including Gradle version and settings (much of this information can be found in Chapter 3).
You can learn more about developing for Android by visiting the following locations: