Xamarin
Xamarin, short for Xamarin.Forms, is a cross-platform framework for building native mobile applications using C# and the .NET ecosystem. It allows developers to write a single codebase that runs on iOS, Android, and Windows devices while providing access to native APIs, UI controls, and hardware features.
ASP.NET
ASP.NET, short for Active Server Pages .NET, is a web application and services framework from Microsoft used for building dynamic, data‑driven websites, APIs, and real‑time web applications that run on the .NET developer platform. You can install and begin developing with ASP.NET by downloading the free and cross‑platform .NET SDK, which includes tooling such as the command‑line `dotnet` tool and IDE support in editors like Visual Studio (Windows/macOS) or Visual Studio Code.
HTML
HTML, short for Hypertext Markup Language, is the standard markup language used to create and structure content on the web. Developed by Tim Berners-Lee in 1991, HTML can be used directly in any web browser and edited with a simple text editor, or through development environments like Visual Studio Code.