Basics
What GIS is
A map, plus the details stored on each line and point.
GIS means Geographic Information System. In normal words, it is a map that also keeps a list of facts.
A paper map shows where a road or a pipe is. A GIS map shows the same thing, and it stores details with it. A gas pipe can have a material, a size, and a status. Click the pipe and those details come up.
Two parts have to match.
The first part is the picture. That is the line, the point, or the shape on the map. People call this the geometry.
The second part is the table. Each row in the table belongs to one thing on the map. The columns are the facts: material, date, size, status, and so on. People call these attributes.
If the line is in the right place but the material is wrong, the map is still wrong. If the facts are right but the line is drawn on the wrong street, the map is still wrong.
People use GIS when the place matters. A city uses it for roads, parcels, and water pipes. A gas company uses it for mains and service lines. A delivery company uses it to see stops on a route.
GIS is not the same as a picture of a map. A picture cannot be searched. In GIS you can ask a simple question: show me every steel service on this street. The map answers from the table, not from someone guessing.
The hard part is not drawing the line. The hard part is keeping the facts true after the work in the field changes.