Himanshu:
I understand your confusion. The Project Management Plan is indeed a compilation of all of the other suib-plans (i.e. risk management plan, resource management plan, etc.). However, all areas are interconnected and have influence on each other to varying degrees (i.e. risk management will influence cost management and so on). With that in mind, the entire project plan will influence each of the other areas.
It's a little confusing at first, but it makes sense as you get deeper into understanding the PMBOK Guide.
Harry