What does npm start do in nodejs

When you issue the command npm start from the root directory of your nodejs project, node will look for a scripts object in your package.json file. If found, it will look for a script with the key start and run the command specified as its value.

If your package.json does not have any scripts object or if the scripts object does not have a start key, it will run the command node server.js instead.

Npm scripts are pretty useful because they let you group together and run logically related commands. e.g. linters, minifiers etc.