No. One of the setting in the Task Information dialog is to "Roll up" a task to the summary bar. That setting superimposes the bar for the selected tasks on the Summary Bar in the Gantt chart.

The rollup field (yes/no) simply indicates whether that option in the Task Information dialog is selected.

I hope this helps.

Thanks but I didnt understand what you mean by

[quote=JulieS;32431]That setting superimposes the bar for the selected tasks on the Summary Bar in the Gantt chart.

quote]

can you explain further if possible? thanks

The best way to understand this is to see what the option does. Create a summary tasks with two subtasks. Roll up one of the subtasks and you'll see the subtask bar appear over the summary task bar in the Gantt chart.