Configs are based on environments and placed inside configs directory.
After run gulp dev or gulp build file app/scripts/configs/config.js will be created.
This file contains constants for your angular.module.
Constants are generated depending on your NODE_ENV (default: local).
Constants gets from configs/constants.
Connecting configs from command console:
$ gulp dev --env=staging
or
$ gulp build --env=production
Also you can add your own config file to configs/constants and use. For more info about configs see: gulp-ng-config