[Zope] Db connectivity with zope

The Zope Experts, I am a new user in zope, then there is a need for me to incorporate an existing database of an org. into their newly design website so that user can query the database. Presently i don't know any single thing on how to do this. But before i started craking my brain i want to you to give me the fundamental concept of how this thing work. Tkanks in anticipation for your supports. Hamzat kamal