Usually, Yin and Yang are thought of as opposites but they're not actually opposing one another in Daoism, they're forces that coexist and complement one another being interconnected and fundamentally inseparable. Like the faces of a coin, two parts of a whole that can never be taken apart. They can give rise to each other and bring out the best in one another or overshadow and eclipse the other but they're never really gone from each other. These can be forces that build upon one another and become more than their separate parts but always form a duality. For example day and night, without the concept of the day, there isn't a concept of night. Light and dark, hot and cold, fire and water, positive and negative the list of examples can go on and on. Yin is thought of as the passive principle and Yang is thought of as the active. So Yin and Yang and all of the analogies I've mentioned as dualities can be thought of as cycles, or processes. Reflecting back upon the day and night analogy, at the end of the day when you're tired and ready to sleep, you find yourself at the precipice of the night and when you make it through the night and wake up rested, the new day is always there waiting for you. Or if you're like me and have insomnia you realize that looking at the clock at 10 pm and then again at 10 am lets you know there's no real difference between not being able to sleep at 10 pm or 10 am and the day and night bleed together not being all that different. The two are never really gone from each other even though we think of "day and night" as separate, they always lead into the other. When a tree grows and reaches for the sky to find the sun a Yang action, it eventually drops it's fruit back to the earth to be reborn as a whole new tree a Yin action then the sapling that blooms from the earth grows into a tree a Yang action and it repeats ad infinitum. Personally, I love how Bruce Lee said: "It's a process of continuing growth." That simple phrase even though he might not have been talking about the concept directly at that moment it truly epitomizes the concept of Yin and Yang a constant cycle of working and building and changing like the day and the night leading into one another. Extrapolating on all of this Wuji is basically nothingness, making it synonymous with infinity. If you think of an empty void it can span on and on forever. In the context of Yin-Yang, it is thought of like the primordial universe so it could, in theory, be equated to the universe before the Big Bang if we toss in some science. It's emptiness. It's like a cup, a teapot, or a bottle before anything is put into it. There's nothing inside, but it has the potential to hold within it anything imaginable. Out of Wuji or nothingness, springs forth Taiji everything, the ten thousand things, etc what gets put into the empty cup. From this point, Yin and Yang come forth, everything carries Yin and embraces Yang. If we look at the cup again the empty space in the cup is Yin, and then what is put into the cup is Yang. "Being and non-being produce each other" just as the dead tree that nourishes the ground becomes nothing, it brings rise to everything by returning it's self to the ground. It's the same with humans, well before the concept of embalming. The earth feeds us while we are alive and we fed the earth with our deaths when we became nothing. Yin-Yang reveals the dualities of the Oneness but they're not truly opposites instead just complimentary forces in harmony. "One begot two. Two begot three. And three begot the ten thousand things." My personal philosophy is influenced heavily by Bruce Lee, who was influenced heavily by Daoism. You need to flow with the way, "Empty your mind, be formless, shapeless like water. Now you put water in a cup, it becomes the cup; You put water into a bottle it becomes the bottle; You put it in a teapot it becomes the teapot. Now water can flow or it can crash. Be water, my friend." If I were to rephrase that iconic quote in my own words for the context of this training I feel like I'd say "Be Yin and embrace Yang. Let your mind be Yin, while your body becomes Yang. While your mind is empty, formless, and shapeless keep your body active and never at rest be ever-changing and unpredictable. An empty mind can be anything you need it to be just like Wuji, nothing can be anything it wants as Taiji springs forth." Obviously, he said it much better than I ever in my life could, but that's what I personally take from Daoism and what I know about it for everyone else it might be different.
With the Naruto World, there's chakra an energy everyone alive produces brought on by the consumption of the chakra fruit of the God Tree. This bigger energy chakra is itself a duality. It's two separate concepts that come together to create something much bigger. These forces are spiritual and physical energies that are molded and used together to play off of and bring out the best in the other. So imagination, meditation, thought, study all become spiritual energy, whereas exercise, movement, fighting etc becomes physical energy. This goes back to Yin and Yang, Yin is passive, Yang is active so by doing passive activities like studying, thinking, or meditating you'll raise your aptitude for the spiritual and if you exercise or fight you'll increase your aptitude for Yang. These two energies combine together into chakra and then from that chakra you are able to mold and manipulate your chakra so that you eclipse one with the other creating Yin energy or Yang energy from it. Yang relates to the physical and is created when a being's physical energy far outweighs that of the spiritual energy it goes back all the way to the Taijitu symbol in my opinion where there is always Yin inside Yang or Yang inside Yin with the two never being completely separate. However to truly learn and master Yin-Yang one must learn both, because "style separates man." There's a small amount of Yin, inside Yang so to produce Yang energy you merely outweigh your Yin, to Yang ratio in favor of the latter. Yang energy is life energy and thus it's abilities revolve heavily around life, the stages of life, aging, peak conditioning, transformation, sentience etc. It's an extremely hot energy, if you were to touch it, it would be like white hot-fire and this is shown in techniques that reference its white-hot whispy nature. Good examples of what it seems like or could do are Akimichi, Sage Transformation, and Inorganic Reincarnation, as well as One's Own Life Reincarnation that technique Chiyo, could use, or Medical Ninjutsu. So now that you have Yang energy from manipulating your chakra the user literally "can breathe life into form." with it. What this means is you are able to manipulate life for example Birth of Nature being able to grow trees to their mature nature. This is like bringing a human to peak condition which is another thing Yang can do, but instead done with trees showing it can work with any living thing. You can heal living beings on par with or even better than Medical Ninjutsu eg Touch of the Sun bringing a person back to peak condition and even regrowing limbs. I have techniques that mimick this via Sage Transformation but even that pales in comparison to what Yang can do saving a person from even the EIG. It can grant genuine sentience and consciousness to constructs, creatures, and elements a la Change into Hell conveying it's similarities to Inorganic Reincarnation. It can be used to alter the strength or speed output of a person, Power of the Sun, Yang Mode etc, or change the body via transformations like Ring of Hell. A good comparison of these transformation based abilities is the Akimichi clan since their transformations revolve around Yang in some way. It shows that Yang has transformative properties to it as life is a process of transformation from a child, to teen, to adult, to death. It can also poison people causing their vitality to degenerate for example 8 Branched Giant Snake or White Tiger both having effects that poison or pollute the opponent's body with Yang energy. This detrimental effect is because the opponent is flooded with Yang energy which is a very volatile and energized substance. They are also unable to control or temper it causing degenerating effects on their body and chakra system. Honestly, the limits are varying but I like what ZK said in his Yin thread "it heals and makes shit stronger" because that's basically what it can do in our RP boiled down to it's easiest to understand properties. Finishing Yang training and specializing in Yang grants the user more aptitude at manipulating their Yang energy with a surplus of life energy/vitality and their chakra giving them an additional 1000 chakra. It also reduces the blunt damage of techniques and attacks by 40 and allows the specialist to take no damage from the recoil of Forbidden rank techniques however they still suffer the effects.
Keep in mind I don't pretend to know everything, or even be that smart so I'm sure I've missed a lot. Especially on the Daoism side.