In-app notifications and push notifications serve distinct purposes in user engagement, with the former appearing within an app while it is open and the latter targeting users outside the app to bring them back. In-app notifications, effectively used, enhance user engagement by pushing users forward in their customer journey and marketing funnel through customized messaging based on user segmentation, behavior, and timing. They are classified into transactional notifications, which guide users, and non-transactional notifications, like promotional offers, and are crucial for maintaining user interest without overwhelming them. Best practices for in-app notifications include setting clear goals, segmenting users, testing and optimizing notifications, coordinating with other marketing efforts, avoiding over-communication, and ensuring each notification delivers value. Successful implementation often requires an app marketing platform to identify, target, and analyze user interactions, allowing for strategic and effective communication within the app environment.