Bulls are an intact (not castrated) adult male of the species Bos taurus (cattle).
More muscular and aggressive than the females of the same species (i.e. cows proper), bulls have long been an important symbol in many religions, including for sacrifices.
Bulls are strong, muscular, mature male cows.
Male cows are typically slaughtered at a young age in agricultural production, if not kept for breeding purposes.
Bulls are not castrated (differentiating them from steers) and can therefore be more aggressive, though they often try to flee from stressors rather than fight.
Also contrary to popular belief the color red does not make bulls angry.
In fact, bulls are partially color blind compared to healthy humans, so that they cannot see red.
Cattle lack the red retina receptor and can only see yellow, green, blue, and violet colors.