Maimonides wrote a famous introduction to it, and it is the major source for Halakha, or Jewish Law.
Additions to this work called Tosefta can be found in its companion volume, in which the Amoraim attempt to clarify the words of this work's Tannaim. Originally recorded by Rabbi Judah HaNasi, it is divided into six Sedarim, which are further divided into between 7 and 12 tractates called Masechot. Maimonides wrote a famous introduction to it, and it is the major source for Halakha, or Jewish Law. FTP name this companion volume to the Gemara in the Talmud.
Additions to this work called Tosefta can be found in its companion volume, in which the Amoraim attempt to clarify the words of this work's Tannaim.
{Mishneh}