terminal variable or config in node.js

Let's look at this command

node test/e2e/server.js --env default --config ./test/e2e/adminUI/nightwatch.json --test test/e2e/adminUI/tests/<group>/<test>

I'm confused how it worked. The source of above command come from here https://github.com/keystonejs/keystone/tree/master/test/e2e/routes, how do I find out what is --env default or --config? or --test? To be honest I have no clue how those things work.

I know node scripts and how to use npm run but I guess its a different thing?