A rainforest is a type of forest characterized by high annual rainfall, typically more than 80 inches (about 200 centimeters) per year, and a warm, humid climate. It is dominated by tall, broad-leaved evergreen trees that form a continuous, dense canopy blocking much of the sunlight from reaching the ground below. Rainforests are primarily found in tropical and subtropical regions near the equator, such as the Amazon Basin in South America, Central Africa, Southeast Asia, and parts of Australia. They are home to immense biodiversity, harboring about 80 percent of the world's terrestrial species, including a wide variety of plants, animals, and microorganisms. Rainforests typically have several layered structures such as the canopy, understory, and forest floor, each supporting unique ecosystems. Besides tropical rainforests, there are also temperate rainforests, which are cooler and less extensive. These ecosystems play crucial roles in the global environment, including acting as carbon sinks and sources of oxygen, as well as providing vital resources for humans and wildlife. Rainforests can also include variations like "dry rainforests," where there is a seasonal dry period, and their lushness varies accordingly. The floor of rainforests has relatively sparse vegetation due to limited sunlight, but it is rich in decomposing organic matter that recycles nutrients into the soil. Rainforests have been critical to human societies for materials, medicine, and food throughout history and continue to be essential for Earth’s ecological balance and cultural heritage.