ESRI shapefiles are split up into “Shapes” which are split further into “Parts”.
For example: One could think of a college or corporate campus as a group of buildings. The individual buildings could be stored as “Parts” and the entire campus could be stored as a group.
KML files work in a similar fashion, although the terminology is different. In a KML file, the “Shape” is termed “Placemark” and the “Part” is termed by its data type (ie. “Polygon”).