In the Hedgehog Concept three circles are used to help you to identify what you should focus your biggest effort on accomplishing. At the intersection of the three circles is your hedgehog concept. The three circles are: 1) What you can be best in the world at. 2) What drives your economic engine. 3) What you are most passionate about.
Remember the fox who wants to catch the hedgehog schemes and plans and always loses. The hedgehog is good at one thing and that is survival. That one thing for you is found at that intersection of the three circles and that is where you should pull your own or your organization's BHAG. The BHAG is that Big Hairy Audacious Goal that is easy for you and your people to understand. It is a mountain. It is difficult to overcome. It is compelling and will bring your people together to try to achieve the BHAG.