Visual Difference can operate in two different modes depending on what it is being used for. Since Visual Difference is both a differencing tool and a merging tool, it has a Differences mode and a Merge mode.

The Differences mode is used to compare revisions and display the differences between them. No merging operations are available in the Differences mode.

The Merge mode is used for all merging related operations and editing.

You can toggle between the two modes in Visual Difference by selecting File > Differences or File > Merge, or you can click Differences or Merge from the toolbar. A bullet displays next to the mode currently being used.

When you switch from the Differences mode to the Merge mode, the Reassign Merge Roles dialog box displays. This dialog box allows you to specify which revision you want as the Merge From and Merge To.