Project milestones mark specific points along a project's timeline. They are checkpoints that identify when activities or groups of activities have been completed or when a new phase or activity is launched.
To create a Milestone,
- Go to the Project Management tab in Salesforce
- Select the Project from the Project list in Gantt
- Click the + button, you see a popup screen for creating Milestone
- Enter the Title, select Type as Milestone, add the Start date,
- Click the Done button,
- The Milestone is created and you see it in the Gantt chart as in the 2nd screenshot below
