This topic applies to "regular" tasks - not iterative work tasks. See Using Tasks for Iterative Work.
Task dates are determined by the project calendar and the task duration as follows:
the task Start Date will be set to the project’s Schedule From Date (using the Constraint Type of 'As Soon As Possible'
the task Target Date will be the date arrived at by starting from the Start Date and adding the default task Duration of one day.
For example, if the Start Date is June 1 (say it's a Monday), the Target Date will be set to June 2.
A task is considered complete when a Complete Date is entered.
How Dates Roll Up
When you enter a Start Date, Target Date or Complete Date for a child task, the date(s) will roll up to the parent task's dates according to the following:
(Note that the Complete Date is not computed until all sub-tasks are complete.)
The start date of any task that has active sub-tasks is automatically set to the start date of its earliest sub-task.
The target date of any task that has active sub-tasks is automatically set to the target date of its latest sub-task.
The complete date of any task that has active sub-tasks is automatically set to the complete date of the latest sub-task complete date when all sub-tasks are complete.
About Percent Complete and Task Dates
For information about calculating % Complete, see Calculating Project and Task % Complete.
% Complete is a system-generated value and cannot be edited by a user. PPM Pro calculates % Complete by Actual Hrs/(Actual Hrs + HTC). If no actual hours have been logged to a task, then the value of % Complete = 0.
% Complete and Complete Date are independent of each other with the exception of when you enter a complete date, PPM Pro sets the task to 100% complete. This means if you estimated 200 hours and only 150 had been logged when the Complete Date was entered, the value of % Complete will be 100, even though there are additional estimated hours.
In addition, Project Managers can adjust the HTC for a task at any time, and when the HTC value = 0, % Complete will be 100%. However, this doesn't necessarily mean your task is complete (needs a task Complete Date). And depending on the timesheet settings, end-users can adjust HTC as well on their timesheets. If HTC rises above zero, % Complete will be adjusted accordingly.
Project dates roll up from tasks as follows: the project Start Date rolls up from the earliest summary task Start Date, and the project Target Date rolls up from the latest summary task End Date. The project Completion Date is the actual date the project ends. When a Complete Date is entered, the project's % Complete field will display 100%