It's called polarity.
THC is polar.
Alcohol is semi-polar meaning it will work for extraction reasons.
Butane, and Hexane are Non-polar. Meaning it bonds to the THC pulling it out of the plant.
Butane will get atleast 80%, while evaporating 99.9% of the butane leaving you an almost pure product.
Alcohol will get atleast 60%, and evaporate at 99.9% as well, but sincei it is semi-polar brings out a lot of chlorophyll too making it black instead of the famous honey color like butane.
CO2 it turns out is non polar, but only liquid under pressure so I would be interested in finding out the extraction method.
Good luck with that one!