Tasks are a set of actions to be executed to complete the Project. When you plan a Project, one of the first things that you need to determine is the timeline. To estimate the overall Project, you should plan all the included Tasks. During the planning, you should determine the start / end dates and the planned effort of the Task.
To plan a Task:
Open the corresponding Task record.
On the Action bar, click Plan Task.
Enter details and click Save.
TIP: You can see visual representation of your Project planning on the Gantt Chart.