– of the Talmud
The Tannaic period was of approximately 320 year duration – from c. 100 BCE – 220 CE
(This is entirely a Pharisee continuum, as is, almost by definition, the entire Talmud.)
Jewish law morphs via the Talmud from the written law* of the Torah (the Old Testament) to the redacted law of the Talmud, to be known as the “Oral Law” (even though, as noted prior, the debates and conclusions are ultimately written down in the Talmud itself).
The debates on the Oral Law, and the decisions of the Tannaim (high level rabbinic scholars who are the actual debaters in the Mishnah), are contained in the Mishnah. [Also, supplemental to the Mishnah are the Baraita and the Tosefta.] Perhaps, see quick–reference Wikipedia online on keyword Talmud for easily–accessible explanations of each: Baraita, Tosefta and, as well, Aggadah].
The Talmud is hierarchical in its redaction. At the apex is the Torah, the Five Books of Moses.
Next comes the Mishnah.
Basically, the Mishnah will interpret the Torah.
Then, the Gemara will interpret the Mishnah.
Mishnah (plus its supplements) + Gemara = the core of the Talmud = “the Shas”
Basically, the conclusions of the Gemara become halacha, or Jewish Law.
There are several important commentaries included in virtually all Talmuds. These commentaries would include, among others, Rashi and Tosefoth.
The major corpus of debate and discussion is the Gemara. The ratio of Mishnah to Gemara discussion is about 1:10.
[Note: the Baraita and Toefta are supplements to the Mishnah, and hierarchically come between the Mishnah and the Gemara.] This is all somewhat difficult to understand, because in reality it is, indeed, complex.
As a historical note on the day–to–day reality, note that many of the Tannaim worked as craftsmen during business hours, as cobblers, charcoal burners, etc. In their parallel Jewish leadership world, they were teachers, rabbinics, judges, leaders of the people, and interlocutors with the Roman Empire.