The framework layer is your abstract layer which can be resused across the implementation layers (application workpools). In simple words, consider the framework layer as the foundation of set of buildings and application layers are buildings built on top of foundation with different specializtions (hieght, size etc.)
All the reusable rules across (or for most application layers) can be placed in Framework workpools (class layer) and create/place rules only to a specific application in application layers.
This helps to reuse common rules, processes, flows across the system which will greately aid during maintanance phase in a project.
Framewok should act as the backbone of the system and it should be abstract. Application layers will reuse the framework layer rules and create instances with specializations.