What are the word in bold? 
Bold marks quotes from Mishnah within in the Talmuds. The Talmuds are commentaries on Mishnah, so a each section starts with a quotation and individual words or phrases are cited wihin the comments.  

What are the dotted underlings?
Individual words with dotted underlining are technical terms. Simple meanings for these terms are available when you hover over these words. These definitions come from the TRENT project, and not from the printed versions of the translations.

What are the words in italics?
Phases or sections in italics in the Tosephta are quotations, usually from the Mishnah, but also from the BIble.
Phrases or sections in italics in the Jerusalem Talmud marks sections of where Hebrew is used instead of Aramaic. 

What is [T1] or [BA3] etc ?
The texts on this site have been marked up with clues about dating the individual rabbis. These dates have been assigned 'automatically', and may occasionally be wrong. This kind of infomation should not be taken as definitive way to date an individual tradition, though it is a good starting point. See the Introductory chapter of Traditions of the Rabbis in the Era of the New Testament.

What is [1.2]? -  References in square brackets
When the text divisions in Hebrew Bavli and the Mishnah MSS differ, the Mishnah is displayed in square brackets as an alternative, so that the Mishnah and Talmud tie up conveniently. (In the original MTR text, the Babli reference is in square brackets instead).

What are the original languages?
The original languages are Hebrew and Aramaic. Mishnah and Tosephta are mainly in a form of Hebrew which can be called Mishnaic Hebrew with occasional phrases in Aramaic. The vocabulary of Mishnaic Hebrew is similar to to Biblical Hebrew, though the grammar has leanings towards to Aramaic. The Talmuds are written in Aramaic though MIshnaic Hebrew is used for quotations of MIshnah and occasional other phrases. Talmudic Aramaic is related to Hebrew but has a significantly different vocabulary and grammar, and the language has developed considerably from the Biblical Aramiac found in Daniel.