In geography, regions are areas broadly divided by physical characteristics (physical geography), human-impact characteristics (human geography), and the interaction of humanity and the environment (environmental geography). Geographic regions and sub-regions are mostly described by their imprecisely defined, and sometimes transitory boundaries, except in human geography, where jurisdiction areas such as national borders are clearly defined in law.Apart from the global continental regions, there are also hydrospheric and atmospheric regions that cover the oceans, and discrete climates above the land and water masses of the planet. The land and water global regions are divided into subregions geographically bounded by large geological features that influence large-scale ecologies, such as plains and features.As a way of describing spatial areas, the concept of regions is important and widely used among the many branches of geography, each of which can describe areas in regional terms. For example, ecoregion is a term used in environmental geography, cultural region in cultural geography, bioregion in biogeography, and so on. The field of geography that studies regions themselves is called regional geography.In the fields of physical geography, ecology, biogeography, zoogeography, and environmental geography, regions tend to be based on natural features such as ecosystems or biotopes, biomes, drainage basins, natural regions, mountain ranges, soil types. Where human geography is concerned, the regions and subregions are described by the discipline of ethnography.A region has its own nature that could not be moved. The first nature is its natural environment (landform, climate, etc.). The second nature is its physical elements complex that were built by people in the past. The third nature is its socio-cultural context that could not be replaced by new immigrants.[citation needed]