A collection or digest of Jewish traditions and explanations of Scripture, forming the text of the Talmud.
Included in the Torah which Moses received on Mount Sinai, was a huge amount of laws regarding all aspects of Jewish life. These explain and elaborate on the precepts hinted at in the chumash. Originally they were handed down verbally from a Rabbi to his students and were not allowed to be written down. During Roman times, the Sages of the day were being murdered by the government at such a high rate that Rabbi Yehuda HaNossi (the leader of Jewry at the time) took the brave step of arranging these laws in order and committing them to writing. This compilation of laws is known as the mishna (plural mishnayos).
From the Jewish word for repetition. It designates the most ancient part of the Talmud, which was put into writing in the eleventh century.