Choose a distance and get a secret destination. Start walking (outside, in real life) and see if you're getting closer or moving further away. Follow the cues to find the pictured location and complete the hunt. Each successful hunt earns you more points for the leaderboard, where you can compete with friends and other hunters around the world. It's a little adventure and great exercise.
Be careful out there! Currently destinations are chosen simply by distance and a safe walking route may not exist. Stay tuned for future updates with smarter destination selection.