The .NET Development Ecosystem involves a variety of tools and libraries for building applications across platforms, including Windows, macOS, and Linux, using the .NET framework and languages such as C#. It includes Windows Presentation Foundation (WPF), Universal Windows Platform (UWP), Xamarin for mobile app development, and web technologies like Blazor and ASP.NET Core. This ecosystem supports desktop, web, and mobile app development, emphasizing cross-platform compatibility and modern design aesthetics.