what is package.json

All npm packages contain a file, usually in the project root, called package. json - this file holds various metadata relevant to the project. This file is used to give information to npm that allows it to identify the project as well as handle the project's dependencies.metadata specific to the project
a web application, Node.js module, or even just a plain JavaScirpt library. 
identifies the project and acts as a baseline for users and contributors 
to get information about the project.
contains a collection of any given project's dependencies