REST API (or RESTful API) is a application programming interface (abbreviated as API) that complies with REST architectural style and is created to allow communication, information flow and interaction with REST (Representational State Transfare) web services. API is used as an interface for communication between two or more programs (or machines) and provides content required from one side to another side (known as consumer and producer; call/request and response).
Getting data from and to database using API is great for building integration with application and retrieving to client all the information in JSON format only once, instead of every time an action occurs on frontend. Yes there are multiple ways to push data to frontend, it can be entity framework, it can be Dapper, it can be T-SQL with procedures layer, it can be REST API, and many many others.
Click through to see how Tomaz does it with Node.Js.