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נבלת בהמה טמאה בכל מקום – whether in the villages or whether in the marketplaces.

The carrion of an unclean beast at all places, and of a clean bird in villages, need intention but do not need to be rendered susceptible. The foods listed in this section are not generally eaten, at least according the first opinion. Therefore, to defile one would need to think about them as food. However, since they are already impure they don't need to be rendered susceptible to impurity. Carrion of an unclean beast, for instance horse carrion, defiles. This mishnah really didn't need to teach this, because it is stated clearly in the Torah. In order to find an innovation in the mishnah the talmud notes that generally less than an olive's worth does not defile because it is too small of an amount. The mishnah is understood as innovating that if 1/2 of an olive's worth of carrion from an unclean beast joins together with a 1/2 of an olive's worth of other unclean food, the two halves join together to defile in the same was as would impure food. If one doesn't think about eating this carrion, it's not considered food because most people don't consider unclean beasts to be food. The carrion of a clean bird is forbidden to eat but it doesn't defile except when in the gullet (see Toharot 1:1). In the villages where there aren't a lot of people evidently most people wouldn't bother eating bird carrion. Therefore, one would specifically have to think about eating it for it to defile.

צריכין מחשבה – for undefined they are not for consumption.

The carrion of a clean beast in all places, and that of a clean bird and also fat in the market places, require neither intention nor to be rendered susceptible. Carrion of a clean beast is forbidden but since most people do eat such animals, it causes food impurity even if one doesn't specifically think about using it for food. It also doesn't need to be made susceptible because carrion is already impure. In market places people will be found to buy carrion of clean birds and forbidden fat. Therefore, they don't need to be thought of as food to defile. And since they are already impure, they don't need contact with liquid to become susceptible.

ואינן צריכין הכשר (and they don’t require preparation) – neither preparation of water nor preparation of a creeping animal/insect [for susceptibility to ritual defilement], for there is no need to have something impure to touch them to defile them, for ultimately they will be impure on their own a grave defilement. And if you should say, it is all right that the carron of a pure/clean fowl and it doesn’t defile other than in the esophagus, it is satisfactory that it requires intention to defile a light defilement. But the carrion of a beast that defiles through contact and through lifting, why do I need intention, for a light defilement, it is an impure body. This manner is answered in the Gemara in the chapter דם שחיטה/The Blood of Slaughter (Chapter 5, Tractate Keritot, folio 21a), as for example, that there is less than an olive’s bulk of carrion, and he attached it to less than an egg’s bulk of food, for whether this one or that one’s an egg’s bulk, and for this reason it requires intention. But nevertheless, it is considered ultimately to defile a grave defilement and doesn’t require preparation, for since it was possible to combine it to be an olive’s bulk.

Rabbi Shimon says: also [the carrion of] the camel, rabbit, hare or pig. Rabbi Shiomon says that people eat camel, hare, rabbit and pig. Therefore, the same rules that apply to carrion of clean meat (cow, sheep, goats) apply to them.

בשווקים – that there is a majority of the people that come to the marketplace, there are many that eat the carrion of a clean fowl, and consume fats.

אינן צריכין לא מחשבה – for they standing for eating.

ולא הכשר – for the carrion of clean fowl ultimately will defile a grave defilement, that will defile clothing in the esophagus, and regarding fat we are speaking of impure fat, that fat defiles like meat, as we learn further on in our chapter (see Mishnah 9), therefore we don’t require preparation.

רבי שמעון אומר אף הגמל וכו' – they (i.e., the carrion of a camel, a rabbit, a hare and a pig) – do not require intention in the marketplaces, for there are many people who consume them, and this is not like the first Tanna/teacher who stated that the carrion of an unclean beast in every place and didn’t exclude these. But the Halakha is not according to Rabbi Shimon.