This is a tutorial about making a REST API using Express and either MySQL or PostgreSQL. There is also a short exmple about using MongoDB.
Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.
A RESTful API is an architectural style for an application program interface (API) that uses HTTP requests to access and use data. That data can be used to GET, PUT, POST and DELETE data types, which refers to the reading, updating, creating and deleting of operations concerning resources.