Here you can see the fields (Screens, Data Elements, and labels) which constitute the Screen and their call characteristics. Each field has a position and a length, and some fields contain data. The information shown here is the same as the -CE Lines tab of the Screen.
If you right-click Map description, you can add a category, add a label, add a Screen, or add a Data Element. These last two choices open a selection box.
Expanding Map description reveals the Screen categories: top (required), repetitive and bottom.
If you expand a field (a Data Element call line), you can see and modify its name and label. Its Attributes contain the same information as the Data Element Definition tab, except the inheritance which can only be specified in the tab.