What are scripts in a file package.json used for and how can they be helpful?

A npm script is a set of user-defined command-line commands that can be executed using a shortcut that is called an alias.

You can define multiple user-defined command-line commands (scripts) and store them to package.json. Later you can execute them using their alias.

Imagine you want to do a backup of your project directory from time to time.

How would you do it?

You could always execute a command-line command similar to "copy c:\yourproject v:\backup". But typing this repeatedly would take too much time. 

To become more efficient you could create a npm script with alias called my-backup and value "copy c:\yourproject v:\backup". After you define the script, you can the execute it by running the following npm command:

npm run my-backup