For this to understand you will need to already have installed and running PhantomJS, how to do that please read here.
https://github.com/Gizra/KnowledgeBase/wiki/Behat-phantomJs-install

With that you will need to run it, open your terminal and write this to make it start

With drush driver for behat you will have some more power, basically drush power to do things. So to make out first drush test, you will need to bring some change in behat.yml file and change some lines.

This just another simple test for behat and mink combo with plain blackbox driver. To log in to a site and do check some behavior you can write this simple test, again no PHP needed for it. You will be logged in and checking what is on people admin page. Add it to your some.feature file and run behat.
 

There is not much documentation and examples of drupal with behat test, so I will start with simplest. I will assume you have installed