Plone logic is wired together by Zope 3 component architecture. It provides "enterprise business logic" engine for Plone.
The architecture provides pluggable system interfaces, adapters, utilities and registries. The wiring of components is done on XML based language called ZCML.
Database drops using Generic setup¶
Zope 3 components act on Python codebase level which is shared by all sites in the same Zope application server process. When you install new add-ons to Plone site, the add-ons modify the site database using GenericSetup framework. GenericSetup is mostly visible as /profiles/default folder and its XML files in your add-on.