Until now, these Mishnayot have been talking about a person who is looking for kaparah (atonement) for unintentional violations of tumah (ritual impurity): walking into the Beit HaMikdash (sanctuary) when he was tameh (ritually impure), or eating korbanot (offerings) when he was tameh. But there is an unintentional aspect to it. Either he didn’t know he was tameh before, or he forgot he was afterwards. There’s a variable here: a person not realizing that he was tameh. Now we’ll talk about what happens if he intentionally violated this isur (prohibition). He, on purpose, walked into the Beit HaMikdash while he was tameh, or he ate a korban while he was tameh. If he knew, there were witnesses, he was warned, and everything happened properly, then the person would be chayav (liable) malkot (lashes). He would have to be given lashes in order to receive kaparah. So our situation will be that he did it on purpose, but there was no ability to give him physical punishment with malkot.
The Mishnah says: For the intentional violation of tumah involving the Beit HaMikdash or korbanot, if the person knew he was tameh and went into the Beit HaMikdash anyway, or ate from a korban anyway, then the goat sacrificed on Yom Kippur (Day of Atonement) inside the sanctuary, together with itzumo shel yom, with Yom Kippur itself, brings kaparah to a certain person. That is, in addition to what we mentioned in the earlier Mishnah—that this korban as well has the ability to give kaparah to somebody who was aware of his tumah before the sin, but not afterwards—he also gets kaparah for intentionally doing an aveirah (sins).
So now we’re going to put all of that behind us—all the tumah violations of the Beit HaMikdash or the korbanot—and then the rest of the perek (chapter) will talk about a person who wants to receive kaparah on Yom Kippur for other types of sins. The Mishnah continues: All other sins in the Torah, the less severe sins, are sins that are not punishable by karet (excision) or the death penalty. The chamurot are those that are punishable by either karet or the death penalty. These include intentional sins and unintentional sins, hoda velo hoda: some of them he became aware of before Kippur, and some of them he never became aware of at all.
And now the Gemara explains that this part of the Mishnah defines the less severe sins we mentioned before: the kalot (less severe sins). What are we talking about by kalot? Aseh velo ta’aseh, positive commandments—that means action-based commands. Lo ta’aseh, negative commandments, where the punishment for them is not anything more severe than malkot. What are the severe sins, or what are the chamurot? Karetot, mitot Beit Din (rabbinical court): sins that are punishable by karet and by being killed by the Beit Din. For all of these averot (transgressions)—everything, pretty much—the sa’ir ha-mishtale’ach, mechaper, the goat that sent to Azazel, brings kaparah to a person for anything that falls within these categories. There are certain averot that don’t fall into them, but for everything that does fall into them, it would bring kaparah, of course, bein adam lachavero (between one person and another). For things that don’t fall into these categories, a person would have to do a little bit more.