A Geographic Information System (GIS) is a system of computer software, hardware and data, personnel that make it possible to enter, manipulate, analyze, and present data, and the information that is tied to a location on the earth's surface. This system comprises of Software, Hardware, Data, and Personnel that make it possible to enter, manipulate, analyze and present information that is tied to a location on the earth's surface. Definition of Geographic Information System (GIS) There are different definitions for Geographic Information System, each developed from a different perspective or disciplinary origin. Some focus on the map connection, some stress the database or the software tool kit and others emphasis applications such as decision support. Defining a GIS can be done by either explaining what it can do (Functions) or by looking at the components. Both are important to really understand a GIS and use it optimally. An analysis of the three letters of the acronym GIS gives a clear picture of what GIS is all about: G: Geographic: Implies an interest in the spatial identity or locality of certain entities on, under or above the surface of the earth. I: Information: Implies the need to be informed in order to make decisions. Data or raw facts are interpreted to create information that is useful for decision-making. S: System: Implies the need for staff, computer hardware and procedures, which can produce the information required for decision-making that is data collection, processing, and presentation. ➢ A GIS is a computer-assisted system for the collection, storage, management, analysis and representation of geo-referenced data to support decision-making. ➢ A geographic information system (GIS) is a computer-based tool for mapping and analyzing things that exist and events that happen on earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps-Environmental Systems Research Institute (Environmental Systems Research Institute-ESRI). ➢ GIS is defined as a computerized system for capture, storage, retrieval, analysis and display of spatial data describing the land attributes and environmental features for a given geographic region, by using modem information technology (Thurgood, 1995). According to this definition, a GIS includes not only computing capability and data, but also managers and users, the organization in which they function and institutional relationships that govern their management and use of information. ➢ A GIS can be defined as a computing application capable of creating, storing, manipulating, visualizing, and analyzing geographic information. It finds its strongest applications in resources management, utilities management, telecommunications, urban and regional planning, vehicle routing and parcel delivery, and in all of the sciences that deal with the surface of the Earth. ➢ Geographic Information System is a system of hardware, software, data, people, organizations and institutional arrangements for collecting, storing, analyzing and disseminating information about areas of the earth.