Gemara

The Gemara (also transliterated Gemora, Gemarah, or, less commonly, Gemorra; from Hebrew, from the Aramaic verb gamar, study) is the component of the Talmud comprising rabbinical analysis of and commentary on the Mishnah.

Divisions
The Gemara is divided into six orders (sedarim). These in turn are divided into tractates (massekhtoth) comprising a total of 63 tractates. These, in turn, are divided into chapters comprising a total of 524 chapters including the sixth chapter of Pirké Avoth, which is a later addition. There are two versions of the Gemara. The Jerusalem Talmud (Talmud Yerushalmi) was compiled by scholars of the Land of Israel, primarily of the academies of Tiberias and Caesarea, and was published between about 350–400 CE. The Talmud Bavli was published about 500 CE by scholars of Babylonia, primarily of the academies of Sura, Pumbedita, and Nehardea. By convention, a reference to the "Gemara" or "Talmud," without further qualification, refers to the Babylonian version. The main compilers were Revina and Rav Ashi.