App analytics allow you to see essential stats about how people are using your app. How long do they use it for? How many abandon the app during registration? Which tasks take too long to complete? If you understand these things, you can plan to improve your app based on what you learn, which can then ensure your app genuinely helps users get things done. In turn, this increases retention and customer satisfaction.
The simplest way to include analytics in your app is to use and SDK such as Flurry, Google Firebase or Amplitude. Then, use Pirate Metrics or the North Star Framework to plan a strategy for capturing analytics in the most valuable way.