Although rainforests cover only a small percentage of Earth's total surface area, they're home to half of the world's plant and animal species. As the name suggests, rainforests are also very wet: They receive more than 70 inches (178 centimeters) of rain each year, on average.
There are many types of rainforests, but they can be split into two general categories: tropical and temperate. Tropical rainforests are hot, lush forests located close to the equator, while the rarer temperate rainforests are found farther north or south of the equator, near coastal areas, according to the NASA Earth Observatory. All of the biggest rainforests on Earth fall into the former category, but we've included the largest temperate rainforest as an honorable mention.
