It is used when you feel Godly and want to bless (fless) someone.
The word was first used in Hyderabad, Pakistan by some students who realized themselves as Gods and formed a religion called Freedom.
In this religion everybody can be a God with a specific quality.
e.g. you can be a "God of Youtube" flessing young people aspiring to be a youtube star ;)
or you can be a "God of Gym" (if you're muscular) and fless the poor people to be muscular and fit!
It can also mean 'detail of guidelines'.
Dumbo: "I keep failing please God I need your blessings"
God of GPA: "You have my flessings, now go and study"