Why are "Fear and Shame" listed among the beautiful cetasikas?

I was wondering how the mental factors of *Fear and Shame* should be understood. Normally I would understand them both as being unwholesome but I guess in Abhidhamma-perspective they have a different meaning. How should they be understood according to the Abhidhamma? They are both listed as belonging to the group of *Beautiful or Moral* cetasikas.