from the behat doc:

All configuration parameters in that file are defined under a profile name root (default: for example). A profile is just a custom name you can use to quickly switch testing configuration by using the --profile option when executing your feature suite.

The default profile is always default. All other profiles inherit parameters from the default profile. If you only need one profile, define all of your parameters under the default: root:

I think that is needed but we can change the name 
check http://docs.behat.org/guides/7.config.html