Jacob wanted his sheep and goats to be stronger than Laban’s, so he wanted the strong babies to be born with funny coloured wool. So whenever the strong sheep and strong goats came to drink water, Jacob put the spotty branches there, and the strong males and strong females joined together to make babies in front of those branches. Later on, when those babies were born, they were strong too, and they had funny coloured wool, so they belonged to Jacob.