Rambam - 1 Chapter a Day

Moreover, he must wear close fitting clothing at the conclusion of the day to make sure that in fact he did conclude the day without experiencing a discharge (i.e., carry out a hefsek taharah) so that he is certain that he begins the seven clean days without discharges.

See Hilchot Issurei Bi’ah 6:8, 11.

I.e., he should not wait until nightfall to carry out this immersion. As stated in Hilchot Issurei Bi’ah 4:6 and Hilchot Mikvaot 1:6, those seeking to regain ritual purity - except a nidah and a woman after childbirth - must immerse during the daytime.
After the immersion, he is tentatively ritually pure. Nevertheless, he should not touch sacrificial foods or enter the Temple that day lest he discover a discharge which would return him to a state of ritual impurity. See Hilchot Mitamei Mishkav UMoshav 5:9.

At that point, his purity is established. If he experienced only two discharges, this is all that is required.

He may then partake of sacrificial food, as stated in Chapter 2, Halachah 6.

I.e., beginning that night, so that the next seven days will be his seven “clean” days.

I.e., after counting four clean days.

I.e., without a discharge.

Although as an initial preference, it is desirable for him to check himself every day, that is not an absolute requirement and, after the fact, as long as he does not find any evidence of a discharge and does check himself on the last day, we assume that he did not experience a discharge. The rationale is that since a man’s natural state is not to experience such discharges, even though he had experienced them previously, we presume that he will not experience further ones. Note the parallel in Hilchot Issurei Bi’ah 6:21.

I.e., as long as he initially checked himself and did so at the end of seven days and did not discover any sign of a discharge in the interim, after the fact, it is acceptable. Note the parallel to ibid.:22.

Or any subsequent day.
The commentaries have raised a question with this ruling, because from the above source, it appears that it is necessary that an inspection be made either on the first or last days of the seven clean days. Both Rav Yosef Corcus and the Kessef Mishneh suggest that it is possible that there is a scribal error in the text of the Mishneh Torah, but admit that the Rambam’s wording does not appear to reflect that.

And he is not obligated to bring a sacrifice. See Chapter 2, Halachah 8.

In Halachah 1.

In which instance, he would ordinarily be considered as a zav.

I.e., the night between the seventh day and the eighth day, when his counting has already been completed.

But instead are considered independently. Were there to have been only one discharge, he would not be considered a zav because of it. He could immerse himself and be purified.

And thus was already obligated to bring a sacrifice.

Although he is impure and must count seven clean days again, at the conclusion of that counting, he brings one sacrifice not two.

For the sacrifice may only be brought on the eighth day.

See Hilchot Bechorot 6:15.

I.e., the night between the eightieth and the eighty-first day.

The commentaries note that in Chapter I, Halachah 8, the Rambam emphasizes that a woman who miscarries within the eighty days associated with the birth or miscarriage of a female must bring only one sacrifice for the two events. He does not explicitly mention, however, the law that would apply if she miscarried on the night of the eighty-first day. Although inferences can be derived from his wording there, that she would have to bring a separate sacrifice, there is no explicit statement to that effect.

Although there is an allusion to her obligation in Leviticus 12:6, it is not explicitly stated there, but rather derived by our Sages in Keritot 8a.

I.e., it is of intermediate status. On one hand, it can lead to zav impurity. On the other hand, since it is only one discharge, it is not considered as that type yet. Therefore it is not reckoned as a zav discharge with regard to the nullification of the seven clean days. As a result, its own significance is not nullified and it can be counted with regard to subsequent zav discharges.

For these are significant as zav discharges. Hence they are considered as nullifying the seven clean days and are not given independent importance, as stated in the previous halachah.

Although the latter two individuals are considered as not able to control their conduct and hence, are absolved from the responsibility of observing all the mitzvot, they still can contract impurity. If they do, they should be purified so as not to spread ritual impurity.

I.e., others bring sacrifices on their behalf.

The expression “it appears to me” connotes a ruling for which the Rambam has no prior explicit Talmudic or Midrashic source, but rather deduced through his own logic. In this instance, these two types of individuals are not obligated to perform any of the mitzvot. Hence, one might think that there is no reason for them to have their sacrifices offered. The Rambam explains that this should be done, lest one desire to feed them sacrificial food. Although they would not be held responsible for the transgression, it is forbidden for another person to feed them food that they are forbidden to eat.

And as stated in Chapter 1, Halachah 5, a child’s sin-offering is eaten.

See Hilchot Ishut 2:14 for a more specific definition of these terms.

Even though there is no concept of such a person contracting ritual impurity because of the release of semen, he may contract ritual impurity because of a zav discharge.

A person whose gender is masked by a piece of flesh.

A person who possess both male and female genital organs. As explained in Hilchot Ishut 2:24-25, with regard to a tumtum, his gender is not known and with regard to an androgynus, there is an unresolved halachic question how to classify such a person. Hence, the stringencies applying to both males and females are applied.

I.e., either because of nidah (menstrual) or zivah (non-menstrual) uterine bleeding.

I.e., either semen or the secretion of a zav. See Hilchot Mitamei Mishkav UMoshav 1:7; Hilchot Nizirut 2:11, where these laws are also stated.

Because of the questions regarding their gender mentioned above. Rav Ovadiah of Bartinura (in his gloss to Zavim 2:1) states that if such a person experiences both zav discharges and zavah bleeding, he is definitely impure.

In which instance, a male is required to bring a sacrifice.

In which instance, a female is required to bring a sacrifice.

Because it is brought because of a doubt.
Based on Hilchot Mitamei Mishkav UMoshav 1:7, Kin’at Eliyahu opines that even if such a person experiences both zav discharges and zavah bleeding, he should not bring a sacrifice, because it is possible to say that a sacrifice may be brought only by a person who is either definitely male or definitely female.

For only the secretion whose type he is counting can cause the counting to be interrupted. If, however, the person sees three discharges while counting for uterine bleeding or experiences uterine bleeding for three days while counting for a zav discharged, he is impure because of the second factor as well and must count seven days to purify himself from this impurity.