There is a BIG difference between common law and a common law SYSTEM, same for civil law.
A common law system is the system we use in Australian courts (adversarial system). Features a judge, jury, legal advocates etc. The judge plays an impartial observer (as you already know) and ensures that the law is upheld. A jury finds guilt or innocence.
A civil law system is the system used in many European countries (France, Greece) (inquisitorial system). The judge plays a more active role in investigating cases, and all evidence is submitted in writing.
I have more detailed notes (this is just off the top of my head) if you need more info send me a personal message