A friend wrote this post on her blog. She has explained it in great detail, I recommend you go through that post before proceeding. Here’s an excerpt -
In the words of a programmer friend, “Project Managers are glorified postmen. All they do is pass on emails from the management to us and progress updates from us to them.” Another friend strongly suspects that the reason his PM looks into his laptop screen so hard is because he is trying to concentrate on beating his own AOE record.
Certain functions within an organization are placed in such a manner that they co-correct each other through symbiosis. For example, Sales and Finance – one drives revenues, the other drives profitability.
PS – Good to know that I am referred to as a programmer 
, I take it as a compliment!
