If you're tracking your health with a Apple watch, you've probably noticed these metrics popping up: stress, HRV (heart rate variability), resting heart rate, sleep quality, and energy levels. They're everywhere in health apps now. But here's the thing—most people don't really understand what they mean or why they matter.

This guide breaks down the science behind stress monitoring and HRV in simple terms. You'll learn what these metrics mean, why they matter for your health, and practical ways to improve them using everyday habits.