In the details page for a project, you can quickly and easily move tasks between workflow task lists. For example, you might put in the "To Do" list tasks that you have just conceived or that are still in the planning stages. Then, when work begins on those tasks, you would move them into the "Working On" list to indicate that work is underway on those tasks. Finally, when work has been finished on the tasks, you would move them into the "Completed" list.
To move a task from one task list to another,
Click and drag the task to the desired list.
You can also change the position of tasks within a list. You do this the same way—by clicking a task and dragging it to the position you want within the list.