Bowl resin is a hodgepodge of nasty stuff.
THC, CBD, other cannabinoid pyrolysis/oxidation products.
Hydrocarbon tars.
Cellulose, sugars, tars from same.
Nitrogenous bases and salts thereof.
Minerals - "ash" - sodium, potassium, magnesium, iron, etc as chlorides, oxides, carbonates, phosphates, or sulfates
Terpenes & terpene oxidates.
Water, light-moecular weight organic compounds.
Resin contains substantially less THC and more products of THC oxidation and breakdown (cannabinol, analogues of THCV, CBD, etc) as well as a higher percentage of nonpsychoactive nasties ("tars", compounds like pyridine, amines etc).