How to understand Use the moleculer.config.js during development or store common options. In production, you can overwrite the values with the environment variables!?

[liaodalin19903]

When I read moleculer runner document :

Use the moleculer.config.js during development or store common options. In production, you can overwrite the values with the environment variables!

I don't understand it,

1.does Use the moleculer.config.js during development mean

moleculer.dev.config.js of

// packages.json
{
    "scripts": {
        "dev": "moleculer-runner --repl --hot --config moleculer.dev.config.js services",

?

2.what's the store common options?

3.does the environment variables means vars in .env?

4.and what's the functionality of the sentence? is it mean we can use custom configure variables?