The document discusses work breakdown structures (WBS), which involve dividing complex projects into simpler, more manageable tasks. A WBS breaks projects down into work packages that can be estimated, supervised, and used to assign responsibilities and allocate resources. It provides a framework for cost estimating, schedule development, and project control. The document outlines different approaches for developing a WBS, such as top-down and brainstorming, and formats for displaying WBS hierarchies.