Onions and Carrots, I haven't forgotten you, it's just that the question is so . . . BIG. To answer it adequately would entail almost writing a book. I'll start with some brush strokes.
There are two main legal systems in the world today: 1) the common law system derived from English law and currently practiced essentially in the former British colonies, and 2) the civil law system practiced in the rest of the world.
In the Common Law system, judges are paramount. A decision from the highest court constitutes law that must be obeyed by the lower courts. The body of laws is formed slowly through the centuries by the accumulation of court precedents.
In the Civil Law system, the legislature is preeminent. Laws are made only by the legislature and a higher court decision is not binding on the lower courts which can always refer to the law (statute) and interpret differently in another case. Laws are codified in a rational manner by subject matter: civil code, criminal code, civil procedure code, etc. France after the Revolution is the birthplace of the Civil Law system. The codes promulgated by Napoleon beginning in 1804 were widely admired for their coherence and simplicity and copied or emulated worldwide. The Dominican Republic adopted the French Codes from its beginnings in 1844.
The two systems have converged with time. In Common Law countries, the legislature has become more and more important as the source of laws. In fact, conservatives in the U.S. want to restrict the power of the courts to make law, based on the same argument used in Revolutionary France that only the elected representatives should have the right to do so.
In civil law countries, despite the legal prohibition of having judge-made law, courts do interpret statutes in such a way that it constitutes new law and lower court judges go by higher court precedents 99% of the time.
So much for today.