Copy editing is nothing but formatting contents without making changes to content of the text.
Difference between Editing & Copy Editing :
Editing refers to making changes to the content of a piece. For instance, you might reorganize, rewrite, revise, reposition -- there's a lot of "re" stuff going on. Typically, it's a very collaborative process with the writer.
Copyediting, on the other hand, involves fewer changes. It focuses more on accuracy, formatting, and sometimes (though not always) proofreading.