ASP.NET is not a mobile app framework in itself (like React Native or Flutter), but it's super useful on the backend for mobile apps.
Cases for ASP.NET in Mobile Dev:
Backend for Mobile Apps
Develop RESTful services using ASP.NET Core Web API
Serve mobile apps with data, user authentication, file uploads, push notifications, etc.
Secure with JWT tokens or OAuth
Mobile Web Apps
Use ASP.NET Core with Razor Pages or MVC to build mobile-friendly websites (responsive via Bootstrap, Tailwind, etc.)
These aren’t "apps" in the App Store sense, but they’re optimized for mobile browsers.
Progressive Web Apps (PWAs)
Build a web app with ASP.NET Core and enhance it with service workers, manifest files, etc.
You get an app-like experience on mobile browsers with offline support and home screen installability.