官方解释：
The .NET Framework (pronounced as "dot net") is a proprietary software framework developed by Microsoft that runs primarily on Microsoft Windows. It was the predominant implementation of the Common Language Infrastructure (CLI) until being superseded by the cross-platform .NET project. It includes a large class library called Framework Class Library (FCL) and provides language interoperability (each language can use code written in other languages) across several programming languages. Programs written for .NET Framework execute in a software environment (in contrast to a hardware environment) named the Common Language Runtime (CLR). The CLR is an application virtual machine that provides services such as security, memory management, and exception handling. As such, computer code written using .NET Framework is called "managed code". FCL and CLR together constitute the .NET Framework.
.NET框架（读作 "dot net"）是微软开发的一个专有软件框架，主要在微软的Windows上运行。在被跨平台的.NET项目取代之前，它是通用语言基础设施（CLI）的主要实现方式。它包括一个被称为框架类库（FCL）的大型类库，并在几种编程语言之间提供语言互操作性（每种语言都可以使用用其他语言编写的代码）。为.NET框架编写的程序在一个名为通用语言运行时（CLR）的软件环境（与硬件环境相反）中执行。CLR是一个应用程序虚拟机，提供安全、内存管理和异常处理等服务。因此，使用.NET框架编写的计算机代码被称为 "托管代码"。FCL和CLR共同构成了.NET框架。
