But the Yom Kippur we read about in the Talmud is not exactly the Yom Kippur Jews experience today. For the last 2,000 years, the Day of Atonement has been observed with prayer and fasting. But in the days when the Temple stood, the heart of Yom Kippur was an elaborate daylong ritual performed by the high priest, the Kohen Gadol. This involved animal sacrifice, confession of sins, and the sprinkling of blood in the Holy of Holies, the innermost chamber of the Temple; and most of Tractate Yoma is consumed with getting the details of this ceremony exactly right. Unlike Eruvin, then, which is intensely practical in its focus on what ordinary Jews can and can’t do on Shabbat, Yoma is highly abstract. It is about a ceremony that hasn’t been performed for 2,000 years and that even then was performed by just one man out of the whole Jewish people.
Earlier Daf Yomi columns are noted here and links.