Diving right in... Introducing Masekhet Yevamot and Seder Nashim! Defining the case of yibum, the Levirate marriage. Defining halitzah. Defining tzarot. Also, beginning with the first mishnah, which presumes knowledge of the basic yibum case, and how co-wives negate the need for yibum for other co-wives - 15 different cases of relationships. Note that the requirement of yibum cancels the prohibition of a woman marrying her husband's brother... And it does not cancel the other illicit sexual relationships. But by virtue of being co-wives, the possibility of negating the prohibition of marrying a brother is often cancelled. Note: Charts will be your friend!! You may want to see Hadran's charts of these 15 cases that make each of them, and the co-wife issues visually accessible: hadran.org.il/wp-content/uploads/2022/03/Yevamot-english.pdf (it's available on Hadran in Hebrew as well).