Torah - (f.; pl. "Torot"); literally, the "Teaching;" the "Constitution" of Judaism and the Jewish People, given to them by G-d at Mt. Sinai, some thirty three hundred years ago. This belief, that the Ten Commandments, the "Aseret HaDibrot," which are the bare outline, as well as the entire text of the "Five Books of Moses" and their explanation, are of Divine Origin, is known as "Torah min HaShamayim;" literally, the Torah comes from Heaven. It is one of the Fundamental Beliefs of Judaism.
The Torah is a "web" of History and Law, the History beginning at the Beginning of Time, and the Law, "preceding" the Beginning of Time, and continuing to the Present and into the Future.
It traces the ancestors of humanity - Adam, "Chava" (Eve), Noach - and the "Avot, the "fathers of the Jewish People," together with the "Imahot," the "mothers of the Jewish People." It shows us an unaltered picture of the interactions of their descendants through Biblical Times, some thirty eight hundred years, beginning with the beginning of recorded history in the Garden of Eden, and ending with the Rebuilding of the Temple in Jerusalem and the End of Prophecy, some two thousand years ago.
The Torah consists of two components: the Written Torah and the Oral Torah. The Written Torah consists of two hundred forty eight Laws of Positive Action ("Mitzvot Aseh") - the "Do's" - and three hundred sixty five Prohibited Activities ("Mitzvot Lo Taaseh") - the "Don'ts". The root word "Aseh" means "to Do."
When did the Jewish People receive the "Oral Torah?" They received it at Sinai, along with the Written Torah. What else do you think Moshe Rabbeinu, Moses our Teacher, was doing up there for forty days and forty nights, neither "eating bread nor drinking water" according to the testimony of the Bible. If not studying the "Oral" Part of the Torah from the Master Teacher, G-d Himself? The Oral Torah is required because without it, its counterpart, the Written Torah, would be incomprehensible.
How would it be incomprehensible? Two examples: one obvious, the second more subtle. First, the Written Torah says in "Devarim" /Deuteronomy 5:8, "Bind them as a 'sign' on your hand, and as a 'totafot' between your eyes." What should be written? What kind of sign? What part of your hand (or is the hand not meant at all)? What in the world is a 'totafot?' Does the Torah mean literally 'between your eyes'? The Oral Torah explains that we have here references to the "Tefilin," the Phylacteries (that's a pretty non-helpful translation); anyway, black "boxes" made of hardened skin, containing parchments upon which are written verses, including the "Kriat Shema" Prayer, "Hear O Israel, the L-rd our G-d; the L-rd is One" ("Devarim"/Deuteronomy 6:4), worn on the biceps (opposite the heart ) and on the forehead (opposite the brain), to unite heart and mind in the Service of G-d.
A second example: The concept of an "eye for an eye, a tooth for a tooth, a hand for a hand, a foot for a foot" as punishment for a physical injury is mentioned in the Written Torah in "Shemot"/Exodus 21:24. This verse has been the basis for criticism of the Torah as a harsh and inhumane document for thousands of years, all based on a misunderstanding of its meaning.
The Oral Law explains that what is meant is a sophisticated five-part monetary form of compensation, consisting of payment for "Damages, Pain, Medical Expenses, Incapacitation, and Mental Anguish" - which underlie many modern "advanced" legal codes? And the expression, "An eye for an eye, etc." means that that is what the perpetrator deserves, if not for the mercy of the Torah and its Author. Ah, you ask, how do you know the Torah means that, and is not to be taken literally? Because the Torah says, "Do not take a ransom for the life of a Murderer, who is wicked to the extent that he must die"; for the murderer, there is no monetary amount that is sufficient to grant him atonement in the eyes of G-d! Only payment with his life will secure that atonement! But for other forms of injury, we will take millions of dollars from the criminal, as a ransom for his eye, hand, or foot; and as atonement, hopefully rendering him a poor man, for his terrible crime!
The Torah is a grand experiment by G-d to see if the human being can live a moral life.
In the Torah, G-d commands the Jewish People, "Be holy, for I, the L-rd your G-d, am Holy." ("VaYikra"/Leviticus 19:2) And teach the rest of humanity that lesson, though they will at first resist to the point of killing you, that the purpose of the Creator in creating the human being was for his highest creature to live his or her life according to true human nature, which is to realize the potential of the "image of G-d" which lies within every human being.