The .NET Framework has two main components: the common
language runtime and the .NET Framework class library.

You can think of the runtime as an agent that manages code
at execution time, providing core services such as memory
management, thread management, and remoting, while also
enforcing strict type safety and other forms of code
accuracy that ensure security and robustness.

The class library, is a comprehensive, object-oriented
collection of reusable types that you can use to develop
applications ranging from traditional command-line or
graphical user interface (GUI) applications to applications
based on the latest innovations provided by ASP.NET, such as
Web Forms and XML Web services. 

The Microsoft .NET Framework is a software framework that
can be installed on computers running Microsoft Windows
operating systems. It includes a large library of coded
solutions to common programming problems and a virtual
machine that manages the execution of programs written
specifically for the framework. The .NET Framework is a key
Microsoft offering and is intended to be used by most new
applications created for the Windows platform.

The framework's Base Class Library provides a large range of
features including user interface, data and data access,
database connectivity, cryptography, web application
development, numeric algorithms, and network communications.
The class library is used by programmers, who combine it
with their own code to produce applications.

Programs written for the .NET Framework execute in a
software environment that manages the program's runtime
requirements. Also part of the .NET Framework, this runtime
environment is known as the Common Language Runtime (CLR).
The CLR provides the appearance of an application virtual
machine so that programmers need not consider the
capabilities of the specific CPU that will execute the
program. The CLR also provides other important services such
as security, memory management, and exception handling. The
class library and the CLR together constitute the .NET
Framework.