1. Trigger: Whether internal or external, the trigger is the tactic you employ to bring users to your app. External triggers, such as push notifications, come from within the app and prompt user action, while internal triggers are abstract and psychological, creating emotional responses like a fear of missing out or the desire to avoid frustrating experiences like going into a physical store.
2. Action: The action is what you want your customers to do after they respond to a trigger. To prompt the right action, designers need to consider the frame of mind users are in after reacting to the trigger: What’s motivating them, and which specific trigger caused their entry?
3. Reward: The reward is what users receive after taking action. Perhaps it’s an entertaining story to share with someone, a cure for their boredom, a discount they’ve unlocked, or a purchased product.
4. Investment: When your app promotes frequent, focused attention, you create a high level of user investment. The time someone spends building a profile—while perhaps earning loyalty points as a reward—creates a subconscious desire to justify the time spent through continual use.
Originally from Nir Eyal, referenced by Bobby Emamian