Mosaic Law is most basically defined as the Law of the Jewish people, inspired by God (YHWH) and delivered to Moses on Mt. Sinai and in the Wilderness as the Israelites wandered for forty years. It consists of not only the well known Ten Commandments, but also approximately 600 other rules and regulations, dealing with everything from what is right and wrong to how to worship and run a business.
Moreover, these legal standards not only covered interactions between God and man, but man and man as well. Unlike our democracy, the Israelites from the very beginning of the nation has held a theocracy, and up until the destruction of Israel by the Romans, maintained it almost solely on Mosaic Law.