An analogy I’ve heard WF themselves use to explain this in their trainings:
Portfolio = file cabinet
Program = folders in the file cabinet
Project = docs in the folders in the file cabinet
A project (doc) should live in a portfolio (cabinet) but doesn’t necessity need a program (folder). If you have a lot of related projects under a portfolio, best to group them in a program.
Common examples:
Portfolio: A client or account or a business line
Program: Segments of work type or campaigns within the account or products under a business line
Project: Actual projects/deliverables within the campaign or for a certain product under its product line program
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