Forests are now considered to be collections of trees as a whole, or large areas of trees. Tropical Rainforest is found around the Equatorial regions, and has perhaps the greatest number of kinds of life of any habitat, and a major role in taking in carbon dioxide and releasing oxygen. Temperate forests are also important.
Old Growth Forests
In California, Indians burned old growth forest with such regularity that there is more old growth today than there was in 1850.
History of the term
The word 'forest' did not used to mean 'a place of trees', however. 'Forest' was a Norman French word, brought to England after 1066. It had the meaning of 'a place of deer (for hunting)'. The Normans designated large areas as 'forest', so that the king and his nobles could hunt there. 'Forest Law' applied, with severe penalties for those 'Saxons' caught killing, or attempting to kill, 'beasts of the chase' (deer, wild boar, etc.). An English forest did not have to be tree-covered: some were mainly wooded forests, like The New Forest, others were mainly moorland, like The Forest of Bowland. Sherwood Forest at the time the Robin Hood legend is set was in fact mainly heathland (heather etc.) and had relatively few, small woods.