What is precedent and what isn’t?

Precedence or controlling law means that a directly higher court’s rulings are binding on its lower courts. Each state is its own sovereign, so only that state’s courts decisions are binding that state. Trial courts are the lowest courts, and those are generally county courts. State appellate courts are next and most states have appellate districts. Only the district (appellate) court and the Supreme Court of the state directly above the county court are binding (or precedence for) a county trial court. The state appellate courts are controlled by that state’s Supreme court.
Federal cases, including Federal Circuit Court cases and Federal District Court cases, are entitled to great weight, but are not controlling on California courts (not precedential). However, the United States Supreme Court is the highest law of the land and is precedent to all states’ cases.