What do you mean by the term project milestone? How would you decide how many milestones to demonstrate on your project plan?

Project milestone:

A milestone is a point at that progress onto the project can be measured. To be helpful milestones must be attached to the completion of important deliverables, as like the acceptance of a Requirements Specification. There requirement to be adequate milestones onto a project plan to permit for adequate control but not so many that their consequence is decreased.