Project managers often are asked, tongue-in-cheek, what do they actually do. I once worked in a department where an employee, who was attached to my team, asked me what he needed to do. This query led to a lengthy explanation of how his job function is performed and what his key contributions needed to be. After a tacit display of gratitude for clarifying some things he had apparently been pondering, he then asked, “and what are you going to do?”
The answer is simple. I am the one would has to either inform the person paying for the project that they will get what they asked for when they asked for it or explain why they will not. To do this I need to be able to apply resources to places that will accomplish our goals and since there are never enough resources (money or people are examples) this takes some skill.
Fortunately, PMI has been around for some time and many people have passed this way before me. The science of Project Management is growing rich with empirical data and scholarly analysis.