A GIS can be viewed in three ways:
1- The Database view
2- The Map view
3- The model view
1.The Database View:
A GIS is a unique kind of database of the world—a geographic database (geodatabase). It is an "Information System for Geography." Fundamentally, a GIS is based on a structured database that describes the world in geographic terms..
Geographic Representations
As part of a GIS geodatabase design, users specify how certain features will be represented. For example, parcels will typically be represented as polygons, streets will be mapped as lines, wells as points, and so on. These features are collected into feature classes in which each collection has a common geographic representation.
Each GIS data set provides a geographic representation of some aspect of the world including Ordered collections of
1-vector-based features (sets of points, lines, and polygons)
2-Raster data sets such as digital elevation models and imagery
3-Networks
4-Terrains and other surfaces
5-Other geographic information such as addresses, place names, geoprocessing models, and cartographic information