That means, he considers his book the Mishna Torah as containing the Oral Law. It is in the third part of deepening one's understanding of the Oral Law that learning the Talmud comes into his program.
Included in the third part of his program is Metaphysics and Physics as he says openly in Mishne Torah. [He explained this is more detail in the Guide. In the beginning of the Guide he explains what he means by Physics and Metaphysics and later explains why they are important.]
So he considers deepening one's understanding of the Mishne Torah as the essence of Gemara.
Thus nowadays what one ought to do after finishing the Mishne Torah straight through [which should take a few weeks at most], is to learn it again with Rav Shach's Avi Ezri, Reb Chaim Soloveitchik's חידושי הרמב''ם, and the books of the disciples of Reb Chaim-- Reb Baruch Ber, and Shimon Shkop. Plus Naphtali Troup (חידושי הגרנ''ט).
I am pleased with seeing this with clarity because it has the benefit of fitting in with how I tend to learn the Gemara--that is to concentrate on one sugia at a time. That is-- to spend a great deal of time on one sugia (subject) which generally includes a few tosphots and a chapter or two in the Rambam plus the portion of the Avi Ezri or Chidushei HaRambam that happen to deal with that particular sugia.
It is nice to see that this in fact fits in exactly with what the Rambam was saying anyway before I even realized that this is exactly what the the Rambam was saying to do.
Seeing this also has the advantage that it fits with something secret the daughter of Bava Sali told me.And also it fits with my parents idea about Torah.