What is .NetFramework ?
The .NET Framework Includes the Common Language Runtime (CLR) and the .NET Framework class library,Metadata, Manifeast. The CLR is a standard foundation for building a range of new applications, while the .NET Framework class library provides standard implementations of many new services for CLR-based applications.

Major difference amoung the Frameworks at a glance
Framework 1.1	Framework 2.0	Framework 3.0
	Webparts (a new thing) Transact