What does Genesis 38:2 mean?

Abraham's offspring had been told not to take wives from the land of Canaan (Genesis 28:1). This was due to issues of idol worship: later, God would make it explicitly against His law to assimilate with the people of the land which God had promised to Israel (Deuteronomy 7:1–4). Abraham went out of his way to get Isaac a wife from outside of the land (Genesis 24:1–4), and Isaac and Rebekah were not pleased with Esau's Canaanite wives (Genesis 26:34; 27:46). Jacob, as well, had taken wives from his mother's homeland and not from the Canaanite peoples (Genesis 29:10–12).

Apparently defying this directive, Judah takes a Canaanite woman, the daughter of a man named Shua, presumably as his wife. Marriage is not explicitly mentioned but seems to be implied. Judah (Genesis 29:25) has recently conspired with his brothers to sell their younger sibling, Joseph, to slave traders (Genesis 37:26–28). For reasons unknown, Judah then moved away from his brothers and the rest of the family at Hebron to live in a town called Adullam (Genesis 38:1).