Geography is unique in bridging the social sciences and the natural sciences. There are two main branches of geography: human geography and physical geography. Human geography is concerned with the spatial aspects of human existence. Physical geographers study patterns of climates, landforms, vegetation, soils, and water. Geographers use many tools and techniques in their work, and geographic technologies are increasingly important for understanding our complex world. They include Geographic Information Systems (GIS), Remote Sensing, Global Positioning Systems (GPS), and online mapping such as Google Earth.