What does 1 Chronicles 2:3 mean?

Judah's sons were Er, Onan, and Shelah. These three were born to him by Bath-shua, a Canaanite woman. Judah's oldest, Er, did what was wrong in God's eyes, so God put him to death. 1 Chronicles 2:3 - Modern Text Bible

(Judah's line is detailed, including the story of his oldest son, Er, whose wrongdoing led to his death.)