A diff is a view that shows the differences between two versions of a file. It is like comparing two drafts with changed lines highlighted so you can see what was added or removed.
Before reviewing an AI coding assistant's work, you can look at the diff to understand which files it changed. This makes it easier to catch an unexpected edit before saving or sharing it.
A diff shows textual changes, but it cannot decide whether the changes are correct. Read the surrounding context and test the behavior that matters.