What exactly is procedural modeling?

Procedural modeling means that 3D geometries and textures are constructed using rules (procedures) instead of labor-intensive manual modeling. A single procedural rule can be used to generate many 3D models. For example, the rule can use feature attribute information stored in GIS data—such as the number of floors, roof type, wall material type, and son on—to generate a series of alternate 3D models that accurately represent the properties of each feature. The more attributes you have, the more accurate the generated model can be.