Iterable is a customer communication platform that allows marketers to design sophisticated multi-channel journeys (email, SMS, push, in-app) triggered by user events. A journey might start when a user signs up, branch based on product they viewed, send personalized sequences, and end when they convert or unsubscribe. Iterable handles segmentation (who gets what journey), personalization (insert customer name, purchase history), A/B testing (which subject line wins), and analytics (open rate, click rate, conversion).