what is npm install

npm install npm@latest -gnpm is a package manager for the JavaScript programming language.

It is the default package manager for the JavaScript runtime environment Node.js

It consists of a command line client, also called npm, and an online database
of public and paid-for private packages, called the npm registry.node -vnpm install package-name

To save as a dependency:
npm install package-name --savenpm install module-name
npm i module-name
puts module-name package (js library file) 
into node_modules folder
so you can require it in node app