Vegetation analysis has five main objectives, namely: an understanding of the plant communities of an area, country or continent; how these communities are related to one another; how they relate to and express their environments; how individual plant species are distributed within these communities; and how the communities develop and function as organised living systems. Vegetation analysis is primarily a field study which relies upon careful observation, the collection of accurate data and a certain amount of intuitive decision-making by the observer. The spatial distribution of individuals of the component species of a vegetation sample confer a pattern on each species and give the vegetation as a whole a horizontal structure. The biogeographer is mainly interested in two aspects of vegetation description: the physiognomy of the vegetation, and its floristic composition. Several major treatments of vegetation at a global scale use no formal classification system while others prefer the ecosystem-type to the term formation.