Coconut（椰子）is an unusual food for many reasons. It is one of the largest edible seeds produced by any plant. Its unusual contents also make it unique in the seed world—it consists of both "meat" and "water" inside. The coconut meat is the white substance with which we are all familiar, as it is used extensively for cooking and flavorings; the coconut water is a white and sweet liquid.Portuguese（葡萄牙的）explorers gave the nut its name in the 15th century, referring to it as coco, meaning "ghost" in their language. The outside appearance of coconuts reminded them of a ghost's face, and the tree has had that name ever since.The coconut has varied uses. It is used to make various cooking oils for fast-food restaurants around the world to make diet materials. The coconut fluid is a favorite drink in hot climates, providing a cool and refreshing beverage right off the tree. This water is also used by manufacturers of various sports drinks. Even the shell itself has many uses, including animal food and fertilizer.Yet the coconut is also useful in many ways that have nothing to do with food. Coconut oil is used for cosmetics（化妆品）,medicines, and so on. Dried coconut shells are used in many countries as a tool for shining wood floors. The shells are also used for shirt buttons, and are commonly found on Hawaiian clothing. They are even used for musical instruments and bird houses.And all these are only some of the uses found for the coconut fruit. The coconut tree, which produces the nut, also produces many useful things. It's no wonder that the coconut tree has been taken as "the tree of life".What is the passage mainly about?