Short : The kernel handles interaction between the OS and hardware.
Long definition: The kernel handles the basic functions of the
operating system: memory allocation, processallocation, device
input and output, etc.
And not copy, paste etc.
There is a command for copy ( cp) and move ( mv ).
The copy and paste functions, you ask about are functions in
the applications, you use. All that takes place in user space.
The source code : have a look in the application source.
This tool will find all information : http://www.google.com/linux