The Torah is the key text in Judaism. Specifically, it refers to the five books which make up the beginning of the Tanakh, the Hebrew Bible. In a more general sense it may sometimes be used simply to indicate the entire body of Jewish law, including the Tanakh, the midrash and the Talmud.
The five books of the Torah are Genesis, Exodus, Leviticus, Numbers and Deuteronomy. These books are all ascribed to Moses, as told to him directly by God. The Torah gives the history of the world and the Jewish people, as well as the 613 laws passed down to them. Some of the laws of the text are not given directly, but are hinted at sufficiently that later teachers derived the laws and recorded them ultimately in the Talmud.
When the Torah was revealed to Moses is a matter of some debate. Some hold that all five books were given to Moses during his communion with God on Mount Sinai in 1280 BCE. Others believe the books were given to Moses by God throughout his life. Still others believe that the majority of the five books were told to Moses throughout his life, but that some passages — such as those describing Moses' death — were later written by Joshua or some other prophet.
In Orthodox Judaism, it is believed that not only the overall message of the Torah is important, but the actual words and even seemingly minor markings all contain lessons given by God to man. This belief is part of the reason that the text has been so well preserved throughout the millennia.
To ensure a picture-perfect reproduction of the Torah, exacting methods are used to copy the holy text. Copies done this way are known as a sefer Torah. It is written on a special type of parchment known as gevil, treated with flour, wasp enzyme and salt. The complete Torah contains precisely 304,805 letters, with exactly 42 lines per column. The placement of each character is crucial, as is the stylization of the letters. As might be expected, the ability to make a sefer Torah is a highly specialized skill, and throughout history a community's copy has been valued as one of its most precious possessions.
Given the difficulty in creating ritually suitable Torah, printed versions abound, both for personal use and for the use of communities that can't afford a sefer Torah. These printed texts are known as Chumashism, meaning "Book of Five." A Chumash will often contain not only the Torah but also other texts.
The Torah is known by a number of other names as well, the most common being either "The Five Books of Moses" and "The Pentateuch". It and two other large sections make up the Tanakh. Directly following the Torah are the books of the prophets, consisting of eight books and covering the seven major prophets and the 12 minor prophets. After the books of the prophets are the writings, consisting of 11 books, from Psalms to Chronicles. Though the Torah and the accompanying books are in a set order, it is understood that they are not ordered chronologically, and instead are often ordered based on the concepts they address.