The central hexagon represents the 6 areas of childhood development, which form the core of what we continue to build upon as adults.  They are Language, Cognitive, Social (sometimes called Emotional), Adaptive aka. Self Help, Agility which is Movement or Gross Motor Skills, and then Dexterity or Fine Motor Skills.  These correlate directly to the Cardinal Virtues in the following way: 

                                     Dexterity/Agility - Strength                                        
                                    Cognitive/Language - Wisdom                                     
Social/Adaptive -  Love

And as adults, we develop 12 main categories of expertise, though our learning styles may vary each area is developed essentially the same way, through play and practice.  Anyone can achieve mastery of any subject by putting the time into it, however finding ways to really engage with it, and apply that learning in a relevant fashion can make this much more effective.  That is why there is very tangible reinforcement for each of these subjects within the human resource based economy/point system, and also study guides and resources which can be used solo and collaboratively.  This real like 'Skill Tree' can help you identify areas in need of strengthening, or disciplines to cross into to add more depth and perspective to established expertise.  Eventually there will be a personal version, which may be used to track progress, keep notes and impressions, and motivate personal work.  Then there will be a correlating online version with links and study notes, sort of a human wiki where these disciplines can branch indefinitely and supporting multimedia can be shared for easy access to learning.