What does "refactoring" refer to in programming?

Refactoring is the practice of restructuring existing computer code without changing its external behavior. This involves making improvements to the design, structure, and organization of code, which can lead to enhancements in performance and readability. The primary goal of refactoring is to optimize the code while ensuring that it still functions the same way, maintaining its original intent and functionality. As a result, maintaining and updating the code becomes easier and more efficient over time.

The other options describe different aspects of programming or software development but do not accurately capture the essence of refactoring. Debugging focuses on finding and fixing errors within the code. Writing new code from scratch is a different process altogether, often associated with creating new features rather than improving existing code. Creating user documentation relates to explaining how code works for others but does not involve changing the code itself. Therefore, the emphasis on improving performance and code structure without altering functionality aligns perfectly with the definition of refactoring.