He slept with Hagar like she was his wife. Then Hagar found out that she was going to have a baby, so she started rubbishing Sarai all the time, because Sarai didn’t have any kids.
Adam and Eve slept together, like a man does with his wife, and then Eve had a baby boy. Eve said, “God has helped me make another human.” So she gave him the name Cain. That name means make.
Those men that were called the Sons of God, they slept with the pretty women, like men usually sleep with their wives, and then those women had kids called Nefalim. Those Nefalim kids grew up to be big, strong fighting men. They were the great fighters in the stories from a long time ago.