A GIS (Geographic Information System)...
“...lets us visualize, question, analyze, and interpret data to understand relationships, patterns, and trends."
(http://www.esri.com/what-is-gis)
"....is a system designed to capture, store, manipulate, analyze, manage, and present all types of geographical data. The key word to this technology is Geography – this means that some portion of the data is spatial. In other words, data that is in some way referenced to locations on the earth." (http://researchguides.library.wisc.edu/GIS)