What is refactoring primarily concerned with in code development?

Refactoring is primarily concerned with rearranging and restructuring existing code while preserving its original functionality. The goal of refactoring is to improve the internal structure of the code, making it easier to read, maintain, and extend without altering how the code behaves when executed. This means that developers will focus on improving aspects such as code organization, naming conventions, and removing duplicate code, without introducing new features or changing existing behaviors.

This process helps in enhancing code quality, making it less complex and facilitating future modifications. It allows developers to work more efficiently and reduces bugs that can arise from complexity. In contrast, other options involve changing functionality, optimizing performance in a way that may entail significant changes, or removing elements entirely, which does not align with the refactoring concept.