The rapid increase in the number and diversity of mobile devices, coupled with explosive growth in mobile applications, effectively creates huge demand for users' attention. While this has resulted in more app downloads, the truth is that many users who download an app often end up ignoring it -- or even worse, uninstalling it -- oftentimes after just a couple of uses. You may have infrequent users who suddenly become regulars, or vice versa. What causes users to uninstall your app after just 2 uses? What causes regulars to just "stop" suddenly? What defines an engaged user? And how does this definition change across users and across the life of your app? The answer to these questions is "Analytics" -- the ability to instrument your application to log events of interest, and then study patterns of events to detect user behaviors or application-usage insights of interest. In this talk we will provide a general overview of the Analytics support for Android before doing a deep dive into "Firebase Analytics" (FA) as one available solution to this problem. The talk will cover setup and instrumentation of your application for using FA and explore various features with an interactive demo. In particular, we will look at two capabilities: using "custom events" to understand user behaviors ("what") and using "user properties" to then segment that user population ("who") into groups that makes it easier to target, track and evolve subsets who exhibit similar behaviors or interests.