As ISO19107 describes, an aggregate geometry is a geometry composed by a primitive geometry collection. The geometries of this set could be different because, in theory, it can be added some new and delete some existing geometries.

In the next figure we show the aggregate geometry's diagram:

There're 5 sorts of aggregate geometries: MultiPrimitive is an aggregate geometry composed by primitives of any type, whereas the other types have primitive of a specific type. For that, a MultiPoint is an aggregate geometry built only by objects Point. A MultiCurve is an aggregate geometry composed only by objects Curve. And so on.