NPM Init and Start

When you are creating a node project, you need to have package.json. npm init is a convenient way of scaffolding your package.json; you may need to run it everytime you are starting a new project.

npm install, however, installs your dependencies in node_modules folder. You may need to run this everytime you manually add a dependency to your package.json file.

If you need extra information, check here: https://nodesource.com/blog/an-absolute-beginners-guide-to-using-npm/

No, you only have to do npm init when you're first creating a project. It essentially just creates the package.json file (https://docs.npmjs.com/cli/init.html).

And you should only have to run npm install when you first set up a project for local development, or when changes are made to the project's dependencies. So, usually just once, unless you've made changes. (https://docs.npmjs.com/cli/install.html)

npm start is a script that should be defined in your package.json, and you will likely need to run that every time you begin local development on your project.