it is a set of standard resource that any .Net programee 
can take advatage of writeen in any language regardless of 
the programming language it is using. it is the environment 
under which .Net programme runs.

the resources are: 1. OOPS , 2. Security Model , 3. Type 
System , 4. All .Net Base Classes , 5. All .Net FrameWork 
Classes , 5. Execution & Code Management , 6. IL to Native 
Language Translator and otimizers.

its the heart of .NET framework its the engine that runs or 
drives the functionality

CLR means commaon language runtime for the dot net frame 
work.
it is the frame work layer that resides above the operating 
system and handels/ manages the execution of the .net 
applications.our .net programs don't directly communicate 
with the operating system but through CLR.


OUT .NET APPLICATION--->>CLR--->WINDOWS OS

CLR Means Common Language Runtime.Thats Only i know.

Clr in .net will peovide many functionalities like
Language interoperabality
Garbage collection
security and many more functionalities.

common language runtime is responsible memory 
management,starting up threads and process and ending them 
and looking after security at runtime and it unifies 
various frameworks as one need not require to know about 
diffrent languages framework.as CLS(common language 
specification) takes care of converting the code to MSIL
(microsoft intermediate language )later which is converted 
machine code by JIT(just in time compiler)

It is the virtual machine component of .net.
At compile time,a .net compiler converts source code into 
CIL code.
At runtime, the CLR's just in time  compiler converts the 
CIL code into code native compilation

All Languages have runtime and its the responsibility of the
runtime to take care of the code execution of the
program..NET has CLR.
CLR is responsible for GC,CAS,Code Verification,IL