Since I spent most of my early years growing up on my grandfather's farm, I knew how to tell a cow from a bull from a steer.
Cows were usually mostly white with some black spots here and there, although some could be all or mostly black. Bulls were just a bit larger than cows and had a thing in the middle of their tummies, unlike the udders that the cows had. Heifers were smaller than cows, and calves were smaller still. They all lived in the barn nearest to my grandparents' house.
Steers were sort of a reddish brown or a brownish red and lived in the barn nearest to our house next to the pigs. That is, the pig sty was near the steers' barn.
But for those who didn't have the advantage of growing up on a farm, here is a useful guide to telling cows apart from bulls and steers.