Milestones
Assign milestones to workflow states for added control over items as they progress through the workflow. You can track multiple items with milestones by adding them to a project in the Project Management tab.
Note: If you don't see a Milestones tab, it could be that your administrator didn't enable the tab for that workspace, renamed the tab, or you do not have the required permissions. If you're not sure and need help, contact your site administrator.