Understanding difference and merge point markers
Each difference and merge point has a special visual marker in the contributor panes.
Difference markers indicate the type of difference (for example, whether something has been deleted, changed, moved, added, and so on). The current difference is highlighted in each contributor pane by using a separate marker.
Merge point markers indicate whether the merge point has been resolved and whether it is the current merge point.
All markers have hover help (ToolTips). Holding the cursor over a marker indicates what it represents.
You can specify character properties and color differences to further highlight differences and merge points.