For he built up again the high places which Hezekiah his father had destroyed; and he reared up altars for Baal, and made a grove, as did Ahab king of Israel; and worshipped all the host of heaven, and served them. Made a grove - He made Asherah, the Babylonian Melitta or Roman Venus. See 2 Kings 17:10, and the observations at the end of that chapter; and see here on 2 Kings 21:7 (note).
Worshipped all the host of heaven - All the stars and planets, but particularly the sun and the moon.