Plone logic is wired together by Zope 3 component architecture. It provides "enterprise business logic" engine for Plone.
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.