Why a Project Management Section?
The architect and the project manager have to collaborate a lot for a software project to be successful. The architect can collaborate better when they understand some of the things that the project manager is trying to do and how that relates to what the architect is trying to get done.
There are lots of good definitions for what project management is all about. See the project management section of the References page for some examples. What it comes down to is that the project manager is responsible for acquiring and assigning resources to most effectively achieve the goals of the project. They are responsbile for budget, resource scheduling, change management, progress tracking, personnel management and risk management.