The Note Keeper app is made with Room Persistence Library.
The Room persistence library provides an abstraction layer over SQLite to allow for more robust database access while harnessing the full power of SQLite.
The library helps you create a cache of your app's data on a device that's running your app. This cache, which serves as your app's single source of truth, allows users to view a consistent copy of key information within your app, regardless of whether users have an internet connection.
