The three main stages of mobile app marketing are Acquisition, Engagement, and Retention. Acquisition focuses on attracting new users through strategies like app store optimization, advertising, and social media campaigns. Engagement involves encouraging active use of the app through user-friendly design, regular updates, and interactive features. Retention aims to keep users coming back, often through personalized content, push notifications, loyalty programs, and responsive customer support. Each stage is crucial for the long-term success and profitability of the app.