Hi Murali,
The Deliverable checkbox is simply an attribute you can set for a task for custom view or reporting purposes, allowing you to separate those elements of your Task plan that are deliverables from the work that produces them, while tracking progress toward the completion of these deliverables.
For example, you may create a parent task as a deliverable, then the aggregated % complete and planned/actual work of the child tasks reflects how much work has been completed/remains on the deliverable:
Parent Task: Building Blueprint (Deliverable)
Child Task: Architectural Renderings
Child Task: Structural Engineering
Child Task: Electrical and Plumbing Plans
Child Task: HVAC Diagram
Child Task: Client Signoff
In this example, you could track the status of the Building Blueprint deliverable as the necessary work is completed by the various contributors.