What is the exact difference between Fairy Law and Fairy Glitter? From the manga and anime, as well reading their description on Fairy Tail wiki, Fairy Law and Fairy Glitter seem very similar. 

Fairy Law


  When activated, a bright light envelops the area and inflicts massive damage on whoever the caster perceives from their heart as an enemy, leaving friends and bystanders completely unharmed.


Fairy Glitter 


  it is a Magic that rivals Fairy Law and is a radiance of merciless light that denies the existence of nearby foes.


What is the exact difference between these two magic spells?
Fairy Law seems to only works on people who are your enemy and is an area of effect type of spell. This spell seems to draw from the user's internal power.

Fairy Glitter seems to be a single target type of spell. This spell seems to draws power from external sources (sun, stars, moon).