Its an optional command line utility that you may use with PostGraphile which does things like printing out your configuration in a pretty format and using TypeScript to figure out what options are available to you based on the plugins you are using. It is 100% non-essential because all the options are documented in each of the plugins (and also you can use TypeScript auto-complete in your editor), and you can just console.dir() your configuration. You can read about it here: https://postgraphile.org/postgraphile/next/config#viewing-th...