Imagine a world where spatial relationships between people and their physical and human environments, economies, and cultures are made clear in ways that have never before been possible. This is the promise of geographic information systems (GIS). The raster data model divides the same geography into a system of equal-sized grid cells. A geospatial analyst is necessarily a generalist in a world of specialists. This suggests that a broad breadth of interests, training, knowledge, and skills are a necessary prerequisite, both in quantitative analytical techniques. ArcGIS Desktop is a complex suite of applications with several major modules that either run as components within the principal gateway or as standalone applications themselves. These include ArcMap, ArcCatalog, ArcGlobe, and ArcScene. The chapter also presents an overview of the key concepts discussed in this book.