A Geographic Information System (GIS) is a computer system for capturing, storing, analyzing and managing data and associated attributes which are spatially referenced to Earth. GIS allows users to create interactive queries, analyze spatial information, edit data in maps, and present the results of all these operations. The document outlines the key components of a GIS including computer hardware, software modules, and databases for organizing spatial data. It also discusses different methods for inputting existing data, maps, and field observations into a digital GIS format.