This document discusses the applications of Geographic Information Systems (GIS). It begins by defining GIS as a collection of software, hardware, data, and personnel used to store, manipulate, analyze and present geographically referenced information. It then lists some key applications of GIS in transportation, water resource engineering, urban planning, construction, and analysis. For each application area, 1-2 examples are provided to illustrate how GIS can be used, such as analyzing transportation infrastructure and planning, modeling watershed areas and reservoir volumes for dam construction, integrating spatial and attribute data for urban planning, and performing various analyses to support design and management of infrastructure projects.