The tropical rainforest is one of the most distinct and important biomes on Earth. They are mostly found in the equatorial regions on the planet, including Central and South America, the Congo in Africa, and much of southeast Asia. They are characterized by warm weather (64 F at least throughout the year) and excessive rainfall (close to 100 inches a year but that can be exceeded). Most importantly, rainforests are havens for natural biodiversity and global oxygen production.
There are several layers withing the tropical rainforest. Most of the trees lie in the canopy layer (100 to 150 feet above ground). This is where the foliage of most trees lie in what is essentially a constant layer that covers the entire rainforest with a several foot thick layer of tightly packed leaves. This has several effects. For one, it provides strength in numbers. The fact that most of the trees grow to similar heights gives them a certain level of protection against wind and storms. Trees that sit higher than the canopy inhabit the emergent layer and they are more prone to wind damage and lightning strikes.
Another feature of the canopy layer is that it traps about 95% of the available sunlight for photosynthesis. Only about 5% of the sunlight reaches the lower levels. As a result, it is very difficult for newer seedlings to acquire enough energy for growth to become new canopy trees. The canopy trees keep themselves dominant by controlling access to resources this way. Sub-canopy level trees and vegetation have adapted to surviving in this lower light level environment.