npm install installs dependencies into the
node_modules/ directory, for the node project you’re working on. You can call
install on another node.js project (module), to install it as a dependency for your project.
npm run build does nothing unless you specify what “build” does in your package.json file. It lets you perform any necessary building/prep tasks for your project, prior to it being used in another project.
npm build is an internal command and is called by
install commands, according to the documentation for build:
This is the plumbing command called by npm link and npm install.
You will not be calling
npm build normally as it is used internally to build native C/C++ Node addons using node-gyp.