What Is The Use Of Milestones And Deliverables?

MILESTONES AND DELIVERABLES:
Managers need information. As software is intangible, this information can only be provided as document that describes the state of the software being developed. Without this information, it is important to judge progress and cost estimates and schedules cannot be updated.
When planning a project, a series of milestones should be established where a milestone is an end-point of a software process activity. At each milestone, there should be a formal output, such as a report, they can be represented to management. Milestone reports don't need large documents. They may simply be a short report of achievements in a project activity. Milestones should represent the end of a distinct, logical stage in the project. Indefinite milestones such as "Coding 80% complete" which are impossible to validate are useless for project management.
A "deliverable" is a project result that is delivered to the customer. It is usually delivered at the end of some major project phase such as specification, design, etc.
Deliverables are usually milestones but milestones need  not to be deliverables. Milestones may be internal project results that are used by the major project manager to check project progress but which are not delivered to the customers.
To establish milestones, the software process must be broken down into basic activities with associated outputs.

Milestones are used to shortly inform the management about the achievement in the project activities. Or its a report written to the manager to see the progress of the project as it is intangible.