Board Thread:Theories and Speculation/@comment-45444155-20200410191621/@comment-4912646-20200411040232

Unfortunately, we never get a full-on explanation of how Yin and Yang work anywhere in the series, so everything we know about them is pieced together through the limited bits of information we've been given. We're told early in the series, long before Yin and Yang are even mentioned, that chakra is made by combining physical energy and spiritual energy, and during Naruto's senjutsu training it's implied that "normal" chakra contains an equal (or at least near-equal) amount of both. As for how this relates to Yin and Yang: Putting all of this together, it seems that Yin Release uses "special chakra" made up of mostly spiritual energy, from which we can logically conclude that Yang Release must be the opposite.
 * In chapter 207, Shikamaru deduces that Tayuya's technique uses chakra that is almost entirely made up of spiritual energy, with very little physical energy. Based on this, he figures that she must use the same type of "special chakra" that he uses for his clan's secret techniques.
 * In chapter 316, Naruto asks Kakashi which chakra natures are used for Shikamaru's Shadow Imitation Technique, as well as Chōji's Multi-Size Technique, medical ninjutsu, and genjutsu. Kakashi implies that explaining those will be complicated, so Yamato suggests he should teach Naruto about the nature transformations of Yin and Yang another time. This marks the first appearance of either term in the series.
 * In chapter 510, Obito describes Yin Release as "originating from the power of spiritual energy, which governs imagination" and Yang Release as "originating from the power of physical energy, which governs life".
 * Finally, in the fourth databook, it's explicitly confirmed that both genjutsu and Shikamaru's shadow-based techniques are an application of Yin Release, whereas Chōji's techniques are an application of Yang Release. You can read what the databook has to say about Yin and Yang here.