Foundational data is available across all project forms and all Product Family libraries by default.
When data is common to all facets of your organization, then it should be considered Foundational.
Product Family data can only be referenced within its unique Product Family when creating reusable records and/or after manually configuring project forms to allow access to a Product Family.
Product Families provide a way to organize and classify your data in order to make content more manageable. Data considered specific to select aspects of your organization should NOT appear in the Foundation Library. Instead utilize Product Families to increase efficiency and relevancy.
Tip: Data added to the Foundation Library can be re-used within multiple project forms and Product Families without further configuration. Simply edit the Foundation source data in one location and have the changes be reflected across all project forms and Product Families (*approval required). When this concept is applied, it can significantly increase efficiency when administrating data.