What feature allows users to track changes made to a document?

The feature that allows users to track changes made to a document is Change Tracking. This functionality is particularly useful in collaborative environments where multiple users might edit a document. When Change Tracking is enabled, any additions, deletions, or modifications made are highlighted, allowing users to see the history of edits. This feature also typically includes options to accept or reject changes, making it easy to manage revisions and maintain the integrity of the document.

Font styles, while important for document aesthetics, do not contribute to tracking changes. Document Comparison is a tool that allows users to compare two different documents, but it does not track changes incrementally within a single document. Review Mode, although related to document review processes, does not specifically refer to the tracking of changes but rather to the overall environment in which reviews are conducted. Therefore, Change Tracking is the most appropriate answer for tracking changes within a single document.