Rainforests are forests characterized by high rainfall, with definitions setting minimum normal annual rainfall between 1750–2000 mm (68-78 inches).
Rainforests are home to two-thirds of all the living animal and plant species on Earth. It has been estimated [who?] that many hundreds of millions of species of plants, insects and microorganisms are still undiscovered. Tropical rainforests have been called [who?] the "jewels of the Earth," and the "world's largest pharmacy," because of the large number of natural medicines discovered there. Rainforests also supply 28% of the world’s oxygen, processing it through photosynthesis from carbon dioxide.
The undergrowth in a rainforest is restricted in many areas by the lack of sunlight at ground level. This makes it possible to walk through the forest. If the leaf canopy is destroyed or thinned, the ground beneath is soon colonized by a dense, tangled growth of vines, shrubs and small trees called a jungle. The two types of rainforest are:
1. Tropical rainforests are rainforests in the tropics, found near the Equator (between the Tropic of Cancer and Tropic of Capricorn) and present in southeast Asia (Myanmar to Indonesia and Papua New Guinea, northern and eastern Australia), sub-Saharan Africa from Cameroon to the Congo, (Congo Rainforest), South America (the Amazon Rainforest) Central America (Bosawás, southern Yucatán Peninsula-El Peten-Belize-Calakmul), and on many of the Pacific Islands(such as Hawaii). Tropical rainforests have been called the "Earth's lungs," although it is now known that rainforests contribute little net oxygen additions to the atmosphere through photosynthesis.
2. Temperate rainforests are rainforest in temperate regions. They can be found in North America (in the Pacific Northwest, the British Columbia Coast, and in the inland rainforest of the Rocky Mountain Trench east of Prince George), in Europe (parts of the British isles such as the coastal areas of Ireland, and Scotland, southern Norway, parts of the western Balkans along the Adriatic coast, as well as in the North West of Spain and coastal areas of the eastern Black Sea, including Georgia and coastal Turkey), and in East Asia (in southern China, Taiwan, much of Japan and Korea, and on Sakhalin Island and the adjacent Russian Far East coast), and also Australia and New Zealand.
Information taken from:http://en.wikipedia.org/wiki/Rainforest