What does 2 Samuel 14:2 mean?

So Joab sent for a wise woman from Tekoa and told her, 'Pretend you’re in mourning. Dress in black and don’t use any lotions. Act like you’ve been grieving for a long time.' 2 Samuel 14:2 - Modern Text Bible

(Joab comes up with a plan to help David by using a woman skilled in persuasion and drama.)