A cue that prompts you to act. It's often external and visual.
Examples: A red notification bubble, a 'ping' sound, seeing the app icon.
The simple action you take in response to the trigger.
Examples: Opening the app, scrolling the feed, tapping a photo.
The brain gets a hit of dopamine. The reward is unpredictable, which makes it powerful.
Examples: A 'like', a funny video, a nice message... or nothing at all.