Evergrande is — or was — the second-largest real estate company in China. A couple years ago, it was the world's most valuable real estate stock. It's also been involved in an eclectic mix of other businesses, from mineral water to electric cars to pig farming. It even owns a professional soccer team. But recently it's been having a really hard time repaying a mammoth amount of debt, a whopping $300 billion worth.

The Evergrande story is bigger than just one company. It's about China's unsustainable model of economic growth, which has relied on endless investment and a mad, debt-fueled development frenzy in recent years. That model helped China soar, but the country is now experiencing some turbulence.