If a task has child tasks, then it is called a summary task. Many attributes of summary tasks are rolled up from its child tasks. Some of the non trivial attributes are described below.
Start Date (planned/actual/projected)
It is the minimum of planned/actual/projected start date of its children.
Finish Date (planned/actual/projected)
It is the maximum of planned/actual/projected finish date of its children
It is the sum of work of its children.
Constraints are not applicable for summary tasks.
Resources assigned to a summary task will not be factored into the planned cost of the summary task, nor displayed on the resource load charts.
% Complete = (W1×P1 + W2×P2 + ... + Wn×Pn) ÷ (W1 + W2 + ... + Wn)For all n leaf-level descendants where Wi is the work and Pi is the % complete of its ith descendant.
If a summary task has a predecessor, the system considers it to be equivalent to having that predecessor for all its children.
Since the planned start and finish are calculated from its children, summary tasks are always considered to be auto scheduled.
It is the sum of the budget/costs/billing of its children.
It is the working time between the task's start and finish date as per the project's work calendar