Each one of your Nobles has a set of Talents, that differs depending on their assigned role. These Talents can be upgraded through the Noble's profile tab (found in the Family tab). Once all the talents in a Tier are unlocked, you can unlock the next Tier of talents (4 max). 

Higher Tier Talents give additional bonuses (new or improvement of original) and they compliment each Noble's perks depending on their intended functions based on their chosen role.

Some Talents don't just give bonus stats, but they also enable certain actions (e.g. Execute). You can see all the available Talents & their bonuses in a Noble's profile page or even better on a Noble Baby's profile while choosing a role!