This document discusses how brands can build engagement through in-app communication. It outlines several communication channels available, including push notifications, in-app messaging, and text messaging. Push notifications are highlighted as a permission-based, multi-purpose, cost-effective, and trackable option. The document also emphasizes using rich content, personalization, context, and testing to create engaging experiences that can drive business benefits such as increased time in the app and re-engaging dormant users. Specific examples from ABC News and Amazon are provided.