Understand the current state, imagine what a successful future looks like, and how you can measure it.
Why to use? Future state envisioning helps teams align around the vision of a successful future that recognizes the current state without being hampered by it.
When to use? Envision the future state at the beginning of a new project to make sure the team works toward the same, concrete vision.
The following resources provide more information about using this method.
Collaborative Product Design by Austin Govella
Chapter six provides detail on variations and alternatives for using this method.