The Masoretic Text
The standard Hebrew version of the Bible used today and the version found in the Torah scrolls in Synagogues is called the Masoretic Text. The original Torah (Five Books of Moses) is traditionally believed to have been imparted by GOD to Moses in the Sinai about 1000 years Before the Common ERA. Over the course of the next millennia scrolls of the Torah and other collected writings were maintained then lost then found throughout wars and exiles of the Jewish community in Israel.
It is believed and documented in current editions of the Bible that the Prophet Ezra made a final collection several hundred years before the Common Era - fixing the Hebrew Bible or Old Testament as we know it today. However, when the Bible was translated into the Greek (the Septuagint) and became the accepted version and as Jews became scattered across the ancient world through exile, the Hebrew writings got corrupted by many translations and dialectic changes. Around 900 CE the Jewish authorities thought it wise to make a definitive translation of the Torah (the Five Books of Moses) back into Hebrew for consistent scrolls to be used throughout the Jewish world.
To accomplish the task scholars known as Masoretes - from the word Masorah, meaning "tradition" - were chosen to complete the task of making a definitive Hebrew edition. Aside from the scrolls, the rest of the "old Testament" was also translated and transcribed back into Hebrew.
For the Books of Moses, or Torah scroll, the Masoretes added in vowels and cantellations to the sides of the scroll. As the Hebrew language is made up only of consonants and the Torah is really one long sentence that can be sung, these additions provide natural breaks by fixing the words and the rhythm. The Masoretes constructed the scrolls to be faithful to the original Hebrew and set down rules for it's copying. (See Torah Scrolls for further information.) One of the interesting aspects of the Hebrew is that without vowels the words can often be changed within reason, rendering new and insightful understanding to the text.