the differrences between tundra and forest

You could say that they're almost completely opposite. Tundra is located on earth's poles, which receive little sunlight making it extremely cold. Little vegetation can become established because of the permafrost that   
prevents root systems, as well as the winds that clear miles of open land. In contrast, tropical rainforests receive direct and constant sunlight, which evaporates large amounts of water into the atmosphere only to drop back down again. Though rainforests only occupy 3% of the earth, it contains over half of the worlds species - the most diverse biome in the world.