WBS: The Art of Decomposition
A large project is frightening because of its complexity. WBS (Work Breakdown Structure) allows you to "cut the elephant into pieces": break one common goal down into small, understandable tasks.
Why is this needed?
So that nothing is forgotten and labor costs are estimated accurately. When you see a project as a hierarchy of tasks, it becomes clear who is responsible for what and where the project's critical points are.