TORAH SHEBALPEH-----basics

What's the difference between Talmud, Gemorah, and Shas?

All of those are part of Torah Shebal Peh ("The Oral Torah"). When G-d gave the torah to Moshe on Har Sinai, He not only gave him scripture, but also many oral explanations of the scriptures, traditions to pass on to the Jews, as well as a systematic methodology to derive laws ands theological principals from the scriptures which would not be apparent by simply reading them on the surface.

These explanations, derivations, and interpretations - everything given to Moshe on Har Sinai besides the scriptures, as well as any derivative teachings that would result from using the G-d-given methodology of interpreting scriptures - is what we call Torah Shebal Peh.

Torah Shebal Peh is part and parcel of our "bible". Its authority is equal to that of the scriptures. In fact, they are not really two "Torahs" but one Torah with two parts. (Technically, laws explicit in scripture have precedence over laws derived indirectly from scripture, but that is not due to any "inferiority" of the authority of the Oral Law.)

Now you need one more word to define, and then we're ready to answer your post:

The Mishna (lit. "recitation") is the collection of Torah Shebal Peh teachings mostly in matters of Torah law (aka "halachah"), and sometimes, but much less often, in matters of Torah ethics or theology, compiled and sealed by R. Yehuda HaNasi around the year 200 CE. The Torah authorities cited in the Mishna, including R. Yehuda HaNasi himself, are called "Tannaim" (lit. "teachers").

The reason it is called "recitation" is because the Mishna was taught orally, from mouth of teacher to ears of students, as opposed to scripture ("Mikrah") which was written and learned from texts.

Once the Mishna was created, it was subsequently analyzed, explained, and expounded on according to the G-d-given methodology that was handed down generation-to-generation, by the most skilled Judaic scholars in the world. These great and holy sages were called "Amorayim" (lit. "explainers"), and their discussions about the Mishna, as well as other teachings of theirs, are called "Gemora" (lit. "teachings", in Aramaic, which is the language of the Gemora). The conclusive opinions, explanations, and interpretations of the Amoroyim are also part of Torah Shebal Peh.

The Hebrew word for Gemora, "teachings", is "Talmud". (So "Talmud" and "Gemora" are really synonymous, but often the word Talmud is used loosely to describe the collective body of Mishna and Gemora together.)

The activity of the Amorayim, i.e. the creations of the "Gemora" took place in two locations: Eretz Yisroel, and Bavel (currently Iraq). We therefore have two separate yet related bodies of Gemora - the Talmud Bavli ("Babylonian Talmud"), and the Talmud Yerushalmi ("Jerusalem Talmud"). The Talmud Bavli was completed after about 7 generations (!) of Amoraic activity, and the Talmud Yerushalmi after about 5.

The Talmud Bavli has more authority than the Talmud Yerushalmi, and as a rule, when there is a disagreement between them; the opinion of the Talmud Bavli is binding.

As for "shas" - that's a political party in Israel.

Only joking. The Mishna discusses primarily 6 categories of laws, and is compiled in a way that all the laws of each type is consolidated in its own section. Thus, we have 6 "sedorim" (plural of "seder", lit. "arrangement" or "order" - used to describe an organized, planned approach to something. This word is the same as in the "seder" on Passover night. There it describes an orderly execution of the night's Mitzvos). The six Sedorim are:

Zeraim - laws pertaining to agriculture and produce (such as tithes)

Moed - laws pertaining to events and times (such as keeping shabbos, when to pray etc)

Nashim - laws pertaining to relationship between men and women (such as marriage and divorce)

Nezikin - Civil law

Kodshim - Laws pertaining to sacrifices and Mitzvos performed in the Bais Hamikdosh

Taharos - Laws of purity and impurity (such as result from contact with a dead body)

The word "shas" is an acronym for "Shisha sedorim" - "Six Sections". It is used to collectively describe all 6 sections of Mishna and its accompanying Gemora. To avoid confusion, when we refer to the 6 sections of Mishna without the Gemora, we don’t use the abbreviation, but we simply say "Shisha sidrei mishna", or "shisha sedorim".

So when you hear that so-and-so "know all of shas" it means he knows not only all the Mishnas, but also their accompanying Gemoras as well.

Because the Talmud Bavli is the more authoritative of the two Talmuds, it is learned almost exclusively by Torah students today, with only occasional use of the Yerushalmi. Thus, when you hear someone mention "Shas", it would refer to only the Talmud Bavli Gemora, without the Yerushalmi.