Article & Video: Designating a task as a milestone.
Milestones help you identify critical points in your project plan.
A milestone might include the delivery of a product, the completion of a certain phase of the project, or client approval. Click on the arrow in the column header and add the Milestone column. Simply check the box to designate this task as a Milestone. You can also set the task as a Milestone in the Advanced section of the New Task or Edit Task dialog box.
The diamond graphic on the Gantt is a visual indicator the task has been set as a Milestone. The diamond graphic is also displayed on the Projects tab in both the Timeline and Burn-down Charts. You can mouse-over the graphic to see the name of the milestone.