The Four Pillars
The core rule of impact mapping: never ask "what should we build?" until you know whose behavior needs to change. The map is a chain with four links, always in this order:
Everyday example — deciding to get fit
Say your goal is "lose 5kg by summer" (the Why). Who can actually make that happen? Only you (the Who / actor). What do you need to do differently? Eat less sugar and walk daily (the How / impact — a real behavior change). And only then: what tools help you do that? A step-tracker, meal-prep boxes (the What / deliverable). Notice you'd never start by buying gadgets — that's backwards. Impact mapping keeps the same order for products: goal first, gadgets last.
Goal
The business metric you need to move.
Actors
The people who can make the goal succeed or fail.
Impact
The behavior change you want to see in those people.
Deliverable
The feature or tool you actually ship.
Quick check
You work at Spotify and want to drive subscription growth. What role does a "Share lyrics to Instagram" feature play in the map, and what is its impact?