When the Jews entered the Promised Land, it was not empty. Tribes named after the land—the Canaanites (in Hebrew, "Knaanim")—already lived there.
The Canaanite peoples neighbored, interacted with, and warred with the Jewish people from the time of Abraham until almost the early Middle Ages, when their descendants completely disappeared among other peoples. It's possible that some of them, at various points in history, became part of the Jewish people.
The concept of the Canaanites is often surrounded by all sorts of myths, some of which we explore in our new film from the "Peoples of the Bible" series.