GIS (Geographic Information Systems) is a collection of geospatial data that contains information of the data.
While a typical map may represent a road or other feature, the GIS system takes that data to the next level.
A GIS gives the user the ability to take the geospatial data gathered from various sources and analyze that data.
Aside from knowing a line is representing a road, the attributes will also contain information such as, surface type, date road was last paved, date road was built, length of road, etc.
The information that can be recorded regarding a feature is endless.
It also has the capabilities to compare the geospatial relationships of the features contained.