The Gemora explains the reasons for the prohibitions listed in the Mishna. One cannot perform the mitzvah of yibum or chalitza on Yom Tov because there is a concern that it will lead to writing. Rashi states that the worry is that the Beis din (Jewish court of law) will write the contract or documents.

One may not generate any form of consecration on Yom Tov since it resembles a business transaction. Rashi offers two reasons why it is forbidden to conduct business on Yom Tov. Firstly, he cites a verse in Yeshaye which states that it is forbidden to talk about business matters on Yom Tov. A second reason is because business transaction can lead to writing which is Biblically forbidden. (37a)

The Mishna had ruled that one cannot separate terumah and maasros on Yom Tov. Additionally, one cannot bring the terumos to the kohen. The Gemora qualifies this ruling to be referring to terumah which was separated prior to Yom Tov; however chalah may be separated and given to the kohen from dough that is baked on Yom Tov. (37a)