A portfolio canvas is a visual tool that defines and communicates the value streams, solutions, customers, budgets, and key activities and events of a SAFe portfolio. It describes how a solution fits into the overall strategy by showing the value proposition, the customer segments and relationships, the key performance indicators, and the alignment with the strategic themes and the portfolio vision. A portfolio canvas provides business context by helping the portfolio stakeholders understand and align on the portfolio strategy, and by guiding the Agile teams and ARTs in delivering value to the customers and the enterprise.
Reference:
Portfolio Canvas: This article from the Scaled Agile Framework explains the concept and purpose of the portfolio canvas, and how it can be used to define and manage the portfolio strategy and execution.
What is SAFe Portfolio Canvas : What are its Sections and Blocks: This article from StarAgile provides a detailed guide on how to create and use a portfolio canvas, with examples and templates for different types of portfolios.