Formally, .NET is “an open source developer platform, created by Microsoft, for building many different types of applications. You can write .NET apps in C#, F#, Visual C++, or Visual Basic.”

Informally, .NET is the tool that lets you build and run C# programs (we’ll avoid F#, Visual C++, Visual Basic for now).

When you download .NET, you’re really downloading a bunch of programs that:

• Translate your C# code into instructions that a computer can understand
• Provide utilities for building software, like tools for printing text to the screen and finding the current time
• Define a set of data types that make it easier for you to store information in your programs, like text, numbers, and dates