Steps to create an APK (signed and unsigned) which you can install on a device using CLI and share as well:
Problem statement: I've built my app, I can run it on my local emulator (and also on my android device by changing debug server). But, I want to build an apk that I can send to someone without access to development server and I want them to be able to test application.
A more detailed description is also mentioned here: https://facebook.github.io/react-native/docs/signed-apk-android.html