This article discusses the importance of user segmentation for effective product marketing campaigns that drive feature discovery, upsells, and adoption. It identifies seven key user segments to focus on: new users, users who haven't engaged with a core feature, users by persona, lifetime free users, users with low MRR, loyal users, and inactive users. The article also provides examples of successful software companies engaging with these user segments through targeted messaging and personalized experiences. It emphasizes the need for setting up business priorities, tracking user behavior, and using a product adoption tool like Chameleon to deliver in-product messaging to specific user segments.