Room persistence library is an object-relational mapping used on top of SQLite database. Which is mainly introduced to save the app developer time on database. In olden day's every developer used to write 1000+ lines of code to create a database with multiple tables in it.
Google I/O 2017 has come up with ORM methodology in Android for SQLite, It saves the developer time by just using the Model(Pojo) classes a table's and DAO interface for CRUD operations.
ROOM is the part of android Jetpack, which is Android Software components can be used to build great Android Apps