Halakhah: Jewish Law
The root of the Hebrew term used to refer to Jewish law, halakhah, means "go" or "walk." Halakhah, then, is the "way" a Jew is directed to behave in every aspect of life, encompassing civil, criminal, and religious law.
The foundation of Judaism is the Torah (the first five books of the Hebrew Bible, sometimes referred to as “the Five Books of Moses”). "Torah" means "instruction" or "teaching," and like all teaching it requires interpretation and application. Jewish tradition teaches that Moses received the Torah from God at Mount Sinai. The Torah is replete with instructions, directives, statutes, laws, and rules. Most are directed to the Israelites, some to all humanity.
Writing and Talking
The words of the Torah constitute what the rabbinic tradition calls the Written Torah. However, beginning around 400 BCE, teachings emerged based in or connected to the Torah, but not literally evident in the text. This body of teaching is known as the Oral Torah, and rabbinic sources claim that it, too, was revealed at Sinai. Halakhah per se begins with this "Oral Torah."
Some laws in the Torah required procedures for their observance that were not explicit. Sometimes conditions under which Jews were living were so different from earlier periods that the ancient rabbis simply enacted new rules in keeping with the laws of the Torah. This process of developing, interpreting, modifying and enacting rules of conduct is the how halakhah develops. The rabbis of classical talmudic Judaism developed a system of hermeneutic principles by which to interpret the words of the written Torah.