What is .Net framework?

.Net framework is a collection of classes which are highly useful to a developer in the daily routine.
Every language contains its own collection of classes.

Java has a class library under the name of JFC (JAVA function class).
C++ has STL (stand tool library).

In the same way, Microsoft provides a huge collection of pre-written classes  under the name of
.Netframework/Base class library(BCL)/Framework class library(FCL) which are available in all languages which are supported by .Net.

.NET framework is an extension for the existing languages.
The people who are having knowledge of C/C++, there is language available in .NET under the name as C#.NET
which provides the same coding environment as C/C++.

For example

In C/C++ If condition we write as below

if(Condition)
{
   Statements;
}

In C#.NET also we write the if condition in the same format.

For VB6.0 developers VB.NET is there.

In VB6.0 if condition syntax is as below

    If Condition Then
      statements
    End if

In VB.NET also the if condition has the same format. So, the developer never feels like working in a new language.
In this way today MS.NET supports more than 90 languages. In each language this collection of classes library available with more powerful features.