Milestone is a scheduling process that describes the set of related deliverables. These are the significant points in time or an event that mark important moments during the project. This is a best practice for project managers to use a milestone in the project to celebrate something expressive being created. Milestone is one of the components of Gantt chart and you will be able to see them on the project schedules presented as a diamond. These are mainly used for
Starting phase
Ending phase
Fixed dates on plan