.NET is a free, cross-platform, open source developer platform for building many different types of applications. With .NET, you can use multiple languages, editors, and libraries to build for web, mobile, desktop, games, IoT, and more.
You can write .NET apps in C#, F#, or Visual Basic. We will be using C# Language for our training program. C# is a simple, modern, object-oriented, and type-safe programming language
Open Source
Completely free
Cross-Platform
Any App, Any Platform
Performance
Trusted and Secure
For more details about .NET, refer the following site: Microsoft .NET