Task Repeat

If you select a repeat value and the task has a start date or a due date, when the task is completed, a new task will be created with a start date and a due date in the future corresponding on the repeat value you selected.

You either choose to repeat from the due date, then the due date of the completed task will be used to compute the due date of the new task.
Or choose to repeat from the completion date, then the completion date will be used to compute the due date of the new task.