ESRI ArcGIS Suite Print

ArcGIS is the most common GIS software in North America.
The main components of the suite are -

ArcCatalog
Accessing, managing, and creating GIS data and metadata.

ArcMap
Data display, analysis and communicating results via map products.

ArcToolbox
Data conversion, management, processing, and analysis. ArcToolbox is accessed from within either ArcCatalog or ArcMap.

ArcPad
Data collection software for GPS-capture and digitizing.

Licensing Levels
3 different levels of licensing are available: ArcView, ArcEditor and ArcINFO, in increasing order of functionality.
To determine which level licensing is installed, in ArcMap or ArcCatalog choose, Help / About.