A GIS stores information about where things are located and what they are. Based on this data, it can perform a variety of specialized spatial analyses. A GIS easily can measure distances between map features, change scales or examine relationships that describe adjacency, proximity, coincidence, and other spatial characteristics. From a conceptual point of view, a GIS can be thought of as many layers of single factor maps covering the same geographic area and stacked atop one another. A user can decide which layers and area to view or analyze.
Most systems now work with vector and raster data.
There is a wealth of public domain data for Connecticut that can be acquired at no cost. The data are available in formats that can be used with GIS or CAD systems.