The umbrella term GIS software refers to a geographic information system

Geographic Information System

A geographic information system, geographical information science, or geospatial information studies is a system designed to capture, store, manipulate, analyze, manage, and present all types of geographically referenced data...

 application, which is software used to create, manage, analyze and display geospatial data on digital map

Map

A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes....

s. GIS software is an increasingly specialized industry, with applications often specifically designed to meet the needs of certain industries.

GIS software categories

Often it is distinguished between the following types of GIS software:

• Desktop GIS are used to create, edit, manage, analyse and display geographic data. They are sometimes classified into three functionality categories: GIS Editor, GIS Analyst and GIS Viewer.
• Spatial database
  Spatial Database
  A spatial database is a database that is optimized to store and query data that is related to objects in space, including points, lines and polygons. While typical databases can understand various numeric and character types of data, additional functionality needs to be added for databases to...
  
   management systems (Spatial DBMS) are used to store the data, but often also provide analysis and data manipulation functionality.
• WebMap Servers are used to distribute maps over the Internet (see also for the Open Geospatial Consortium
  Open Geospatial Consortium
  The Open Geospatial Consortium , an international voluntary consensus standards organization, originated in 1994. In the OGC, more than 400 commercial, governmental, nonprofit and research organizations worldwide collaborate in a consensus process encouraging development and implementation of open...
  
   standards: WFS and WMS).
• Server GIS provide basically the same functionality as desktop GIS but allow to access this functionality via networks (so-called geoprocessing).
• WebGIS Clients are used for data display and to access analysis and query functionality from Server GIS over the internet or intranet. Usually One distinguishes between Thin and Thick client. Thin clients (e.g. a web browser used to display google maps) provide only display and query functionality while Thick clients (e.g. Google Earth or a Desktop GIS) provide often additional tools for data editing, analysis and display.
• Libraries and Extensions provide additional functionality that is not part of the basic GIS software because it may be not needed by the average user. Such additional functions can cover tools for terrain analysis (e.g. SEXTANTE), tools to read specific data formats (e.g. GDAL and OGR
  GDAL
  GDAL is a library for reading and writing raster geospatial data formats, and is released under the permissive X/MIT style free software license by the Open Source Geospatial Foundation. As a library, it presents a single abstract data model to the calling application for all supported formats...
  
  ), or tools for the cartographic display of geographic data (e.g. PROJ4).
• Mobile GIS are used for data collection in the field.

Tasks accomplished with GIS software

Typical tasks carried out with GIS are:

• viewing / exploring data
• creating data (the dataset is extended)
• editing data (the dataset is modified)
• storing
• conflation (integrating datasets from different sources)
• transforming (into different coordinates systems, different representations, re-sampling - resulting in new representation/format of the same data)
• querying (resulting in a selection from the dataset)
• analysing (resulting in a new dataset, with new information obtained from the original dataset)
• create maps

Further reading

• Longley, P.A., Goodchild, M.F., Maguire, D.J., and D.W. Rhind, Geographic Information Systems and Science. 2nd edition, John Wiley & Sons, 2005.
• Sherman, G.E. Desktop GIS: mapping the planet with open source tools, The Pragmatic Programmers, LLC, 2008.