What does Genesis 38:14 mean?

Tamar took off her widow’s clothes, covered her face with a veil, and sat down at the entrance to Enaim, which is on the way to Timnah. She realized that even though Shelah was grown, Judah hadn’t arranged for her to marry him. Genesis 38:14 - Modern Text Bible

(Tamar sees that Judah isn’t keeping his promise, so she takes matters into her own hands.)