Hi yasu!

npm run dev-server starts in debug mode; it's useful while developing your application as it will provide additional debug info.

npm run start is for running in production mode; debugging functionality is turned off in order to maximise performance.

In production mode, webpack bundles together all the scripts for efficiency, instead of keeping them separate.

http://conoha:3000/ will not work in development mode, because the application is not listening on the public IP.

However, in production mode, the file index.js gets run. You can see the line app.listen(3000);. This is equivalent to app.listen(3000, '0.0.0.0'); which means that it will listen on ALL IP addresses.

Hope this helps! 🙂