A 'north star metric' is business jargon — a single key number a company uses to measure long-term success and align everyone around it. For Spotify it might be 'time spent listening'; for Airbnb, 'nights booked'. If your teenage child uses the phrase they may be picking up startup or career language from YouTube, podcasts or a university module. It is not slang in any youth-cultural sense and carries no hidden meaning. The metaphor comes from the Pole Star, traditionally used by sailors to navigate. It is a concept worth understanding for anyone interested in business or product careers.