The .NET Framework is an essential technology for ASP.NET development. It provides the basic system services that support ASP.NET, as well as Windows Forms development, the new rich client development technology provided by .NET. The .NET Framework consists of two main parts:
1. The common language runtime : It provides a run-time environment for the execution of code written in any .NET language.
2. The .NET Framework class library : It is designed to support the efforts of developers by providing base classes from which developers can inherit.
Click the following link to learn .Net Framework in detail. Microsoft .Net Framework Step by Step