A SAFe portfolio is a collection of development value streams. A development value stream is a long-lived series of steps that an enterprise uses to continuously deliver value to a customer or stakeholder. A development value stream typically consists of one or more ARTs and Solution Trains that build and deliver solutions. A SAFe portfolio aligns and governs one or more development value streams that share a common business mission, vision, strategy, and funding. A SAFe portfolio helps enterprises achieve Lean Portfolio Management, which is one of the core competencies of business agility in SAFe. References: SAFe Portfolio, Development Value Streams