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What is Diff?
Definition
A diff (difference) shows the changes between two texts or files. It highlights added, removed, and modified lines. The unified diff format (prefixing additions with + and deletions with -) is the standard in Git and code review tools.
Why It Matters
Diffs are central to code review, version control, and debugging. Every Git commit, pull request, and merge conflict is expressed as a diff. Understanding diff output helps developers review changes quickly and resolve conflicts correctly.