You can think of geoprocessing as a language, where nouns are geographic data, such as features and tables and rasters, and tools are verbs, such as copy and clip and join. Like any language, there are a handful of nouns and verbs that you need to know to communicate, and this section (and those that follow) introduce you to these common geoprocessing verbs (tools).
The most commonly used GIS tools automate tasks that were historically done manually—compiling new maps by overlaying one on top of the other or physically cutting maps into pieces representing specific study areas, then changing their projection. Some of these manual tasks were so arduous and complex that they held back the dissemination of geographic knowledge and data and were the primary impetus behind the invention of GIS.
Overlay and proximity
The first two sets of commonly used tools answer two of the most basic questions in geography: What's on top of what? and What's near what? The first set of tools is discussed in Overlay analysis, and the second set is discussed in Proximity analysis.
Geographic phenomena are not limited to discrete points, lines, and polygons but include data, such as elevation, slope, rainfall, and temperature, that varies continuously across the earth's surface (or whatever planet or object you're studying). Such continuous data is called a surface and is modeled with rasters and TINs. There is a set of tools to create and analyze surfaces, which are discussed in Surface creation and analysis.
Spatial and nonspatial statistics
One of the axioms of geography is that things that are close together are more similar than things that are farther apart. This axiom forms the basis of powerful spatial statistics tools that allow you to discover and characterize geographic patterns and are described in Statistical analysis, along with standard nonspatial statistical tools, such as minimum, maximum, sum, frequency, mean, and standard deviation.
ArcGIS stores data in easily accessible tables, and the majority of workflows involve some sort of table management, such as adding or deleting fields, creating relationships between tables, or creating features from columns containing coordinates. Table analysis and management describes the basic tools for managing tables.
Selection and extraction
GIS datasets often contain much more data than you need, and a common set of tasks is to reduce or extract data from larger, more complex datasets. Tools for these tasks are discussed in Selecting and extracting data.