Probably just repeating the answer again... BUT
Males have balls
Females have Bud (like an egg ready to be fertilized)
A Hermie HUMAN is a man/woman, meaning they have both sexual organs, but usually not functional as humans are very complex and NOT a plant.
In the case of a pot plant a HERMIE doesn't only have both sex organs, but both sex organs FUNCTION! meaning a SINGLE plant can reproduce on its own.
The reason it occurs IS stress. Many things can stress the plants I'll list em in the jumble of writing below....
Plant and animals... Guess that means everything in the world actually... has INSTINCT in this case its the instinct/will to SURVIVE. If the plant gets stressed by temperature, lighting, physical damage, etc. The plant feels the need to reproduce QUICKER, so instead of waiting for a male it grows its very own BALLS and pollinates itself!!! (and alll other females surround etc.)
This happened to me. TOO my plants I should say.... It was late season the weather turned cold and the plant got desperate (ph of soil was out, no nutes were given, water was scarce, and it was very cold some mornings).