The coconut (Cocos nucifera) is a member of the palm family that grows as a tree, and produces drupes that are commonly called coconuts. Nearly every part of the tree and the coconut are important commercially, though the coconut can only be grow between 26 degrees North and South latitudes. While the origin of the coconut palm is not well delineated, it is commonly thought to come from somewhere in the Indian or Pacific oceans.
The coconut is actually in three layers: Exocarp (the green "skin" which is typically removed for export), Mesocarp (the fibrous husk) and Endocarp. Mature coconuts weigh about three and a half pounds, and have three "eyes" in the base, which are germination pores for the new seedling.
The easiest way to open a coconut is to either drill out or hammer a nail into the eyes. Then wrap the coconut in a towel and hit it with a hammer to fragment it into pieces. The brown shell can be pared away with a small, sharp knife.
Some of the more common uses for parts of the coconut include dyes and a mouthwash from the roots, bridges, drums and canoes from the trunk, mattress stuffing and rope from the fibrous husk, fans and brooms from the leaves, and charcoal from the shell. The shells can be clicked together to make the sound of horse's hooves.
From the immature drupe, the jelly-like flesh can be removed with a spoon and eaten, and the liquid inside (called coconut water) is not only delicious, but also sterile -- it was used in IV bags before the introduction of saline solution.
When the drupe is mature, coconut milk can be made from passing hot water or milk over grated coconut flesh. Coconut milk (which is around 17% fat) will settle into milk and a layer of coconut cream. The flesh itself is edible, and used as a garnish in quite a few southeast Asian cuisines. When the flesh is ground and turned into cakes called copra, it can be pressed to produce an oil higher in saturated fat than butter or lard, which is a staple fat source for much of the world.
The bud branches of the coconut palm can be cut and tapped for sap, which can be drunk straight, or fermented into palm wine. Palm wine can be distilled into arack (which in the Phillipines is called lambanog, and can be artificially colored and flavored in a garish multitude of ways).
Coconut is a common flavoring for rums, as it is a common pairing with the spirit. The aroma of coconut comes from a chemical called gamma-nonalactone - it is fatty/waxy, with a sweet, neutral-floral aroma. Many suntan oils are scented with artificial coconut aroma, so the smell of lesser coconut flavorings can be described as "suntan oil".