Code that is executed by the CLR. Managed code provides 
information (i.e., metadata) to allow the CLR to locate 
methods encoded in assembly modules, store and retrieve 
security information, handle exceptions, and walk the 
program stack. Managed code can access both managed data 
and unmanaged data. Managed data—Memory that is allocated 
and released by the CLR using Garbage Collection. Managed 
data can only be accessed by managed code


2.Code that targets the common language runtime, the 
foundation of the .NET Framework, is known as managed code; 
code that does not target the common language runtime is 
known as unmanaged code. 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 in the 
code. The concept of code management is a fundamental 
principle of the runtime. 

3.Managed code supplies the metadata necessary for the CLR 
to provide services such as memory management, cross-
language integration, code access security, and automatic 
lifetime control of objects. All code based on IL executes 
as managed code. 

4.Code that executes under the CLI execution environment. 
Managed code uses the execution environment for memory 
management, object lifetime, and the basic type-system, 
among other fundamental services.

A code that executed under the instructions of CLR is called
managed code.
A code that execute without the instruction of CLR is called
unmanaged code.

A code which is understandable by CLR is called managed code
A code which is not understandable by CLR is called
unmanaged code

Managed code are execute by CLR,
Unmanaged code are use wrapper class,

Program written in any .net compatible language will go for
compilation for 2times.
In the first compilation of the program, the language
compiler will generate MSIL code which is the managed code. & 

the code generated after the second execution ie by the CLR
is called unmanaged code which is machine understandable and
not by the user.