I'll go more in depth in a few points.
2)Chakra is what ninja use to accomplish their goal. Now for what chakra is, it is the product of molding both physical and spiritual energies. Also, something that I learned from reading Caliburn's Yin-Yang training, is that what makes a distinct chakra signature, for an individual, is the ration and balance of Yin-Yang, and no one has a identical chakra signature to another person. Also chakra has a limited flow, the thing that limit it are the Eight Inner Gates. The gates control how much chakra can be used. If a person goes though proper training they may be able to unlock some gates, thus increasing the amount of chakra, which in turn increases strength, but it comes at a cost, which is reducing the person life span, and putting the person in danger if in continuous usage.
I believe that everyone in NV has chakra, but it the ninja that are capable of using it, they achieve this through training themselves, however not all are capable of properly using it, a green example is Bushy Brows Student, Rock Lee. Lee attempted to train himself in using chakra but miserably failed, this means not all are suited for the job.
3)Taijutsu(and Kenjutsu): Taijutsu otherwise known as hand to hand combat, is a skill that people in NV rely on when in close quarter combats. It's most common usage is the strong fist version, in this version chakra can be used to empower a attack, but it is not necessary though. Also strong fist version relies in force and momentum. Another version of Taijutsu is that of the Hyugas, in the Hyuga version, chakra must be used, it relies on striking the inner points of the body, those points are related to the EIG. In gentle fist, the user closes those points in order to hinder the opponent. And by using basic logic opening them, would lead to overwhelming the opponent. With that we conclude that Taijutsu's effectiveness can be increased though the proper usage of the EIG.
Kenjutsu is commonly forgotten, that is due to the fact that it is rarely used by Ninja, it is more common amongst Samurais. But nevertheless Kenjutsu is a very effective fighting style, it revolves around using weapons, specifically swords, although some have been seen to use different weapons, per example Hiruzen Sarutobi uses a staff.
Genjutsu: It is known as illusionary arts, the art of deception, the art of the strategic. You see, Genjutsu is a way to trap and deceive your opponent, when your opponent is trapped in a Genjutsu that gives the user a tactical advantage. For example a illusion that makes the opponent see himself trapped inside a dome would force the opponent to attempt to destroy the dome.
Genjutsu commonly affects the five senses; Sight, Smell, Taste, Sensation, and Hearing. The most affected senses are Sight, and Sensation. The reason is due to it being more simpler to use, and quite frankly easier. Hearing is not commonly used, it is due to sound related Genjutsu requiring a instrument or Sound release itself. Smell induced genjutsus are also not common, that is due to the user needing to be near the affected person so that the person can get affected, Inuzuka's are at a disadvantage due to their increased sense of smell. Taste related are rarely seen, I personally think if someone where to use a taste related Genjutsu it should be during s meeting where the opponent is eating, that would make it easier to induce the genjutsu without suspicion.
Furthermore genjutsu requires great chakra control, since the user must precisely affect the opponents chakra network. Also Ocular Genjutsu exist, they are used by Uchiha through the usage of their Sharingan. With the increase of tomoes of the sharingan, the better the Genjutsu. Also Kurama clan members can make their Genjutsu real through their HA.
Ps: Shout-out to Keurini even though I spelt her name wrong <_>.
Ninjutsu: Ninjutsu is known as ninja arts, and from that name we know several things, it is used by ninjas, keyword being Ninjas. So ninjutsu is the key to the door of goals of ninja, it is used to accomplish the goals that the ninja desire. This is done through shape and nature manipulation.
Shape manipulation allows the ninja to give a specific form to his chakra, may it be animal, human-like, or an object. Nature manipulation allows the ninja to give the technique certain aspects. Sometimes hand seals are used.
[Aspects, and Hand Seals elaborated below.]
5)
-Water: The element of the calm.[Power depends on concentration and it is the third/fourth fastest element]
-Wind: The free, all reaching element.[Has cutting capabilities, second fastest element]
-Fire: The bringer of destruction element.[Burning attribute, third/fourth fastest element.]
-Earth: The unmovable, resistant element.[Force and density mostly, can derive into mud for example. Slowest element]
-Lightning: The uncontrollable 'outlaw' element.[Has cutting abilities, in addition to paralysis related, Fastest element]
The main elements that exist in NV are 5 to be exact; water, wind, fire, earth, and lightning. Each element is most used in a specific land: Water; Land of Water, Fire; Land of Fire. So on and so forth with the remaining.
Water: It is weak towards Earth due to earth preventing the movements of the water, it is strong towards fire due to water's capability to extinguish.
Wind: It is weak towards fire, since the wind will act as a fuel for it, it is string against lightning since it acts as an insulator.
Fire: Covered in the above.
Earth: It is weak against lightning since it acts as a conductor, as for strength mentioned above.
Lightning: Mentioned above.
As for usage, it is all situational, if I were to begin listening ways to use the elements I won't finish, since for each situation there is a way to use the elements.
6-7) More on them later
8)Now mass comes into play when two solid objects are related, if one is fire and other is earth, mass plays no role in it. But when they are both objects(have a phsical state), the one with the greater mass would win the collision, that is if they had the same size and similar forms, but also velocity and speed must be considered. Now if an object had a bigger size than another, but the same mass, and velocity, then the one that is bigger would prevail, but not completely, the part of it that is equivalent to the second body would be stopped, only the extra parts would continue.
Also sometimes it isn't necessary that the technique with more 'strength' would prevail. For example, my opponent throws 6 Explosive tagged kunais at me, I throw a singe explosive tagged one, the tag detonates when it collides with his, thus scattering the kunias around. Simple examples for now.
9)Hand seals are 'helpers' of a technique, with hand seals, the ninja can mold chakra in a improved manner compared to when their are no hand seals. Also hand seals are used to control and improve the overall performance of a technique. When more hand seals are present it signifies that the technique is harder to perform, but it would most likely have beneficial results. Also when someone gains mastery over a certain element, that person can perform those techniques with reduced number of hand seals, or a single one, or even with one hand like in the case of Haku Yuki.
Naturally it is required to memorize the hand seals in order to perform them, the snake hand seal is attributed to earth release, since the position of the hands are firmly rooted together just as earth is. Also hand seals that differ from the common 12 exist, an example being the cross hand seal, it is used by Naruto to create his shadow clone, another example can be slamming, some techniques require slamming one's hands on a surface, that surface can be the users own hands AKA clapping, or the earth, an example of slamming on earth is Moving Earth Core, or slamming one's hands on a surface to summon objects/animals. Those are not hand seals, but have the same function as hand seals.
10)A KG is a ability that is only present to those who are born into a specific clan/bloodline. The ability will be genetically inherited, however this does not mean that all descendants of the bloodline would have said KG. Naturally there are exceptions, specifically Hyugas, all Hyugas have a Byakugan, I personally believe it's from inbreeding >_>, but Kishi logic differs. In a less perverted mind, it is most likely due to the Gene responsible for the trait being extremely strong. As said before not all will gain their KG, such as Uchihas, Uchihas need to experience a traumatic moment to unlock their sharingan. Other KGs don't rely on Ocular power, for example only those of the Yuki clan can manipulate and create ice release, it is not done through eye powers, but through the combination of two elemental natures being Wind & Water. Also some abilities are unique to only a certain individual like Wood to Hashirama, or Micheal Jackson syndrome special snake/kinjutsu related techniques to Orochimaru.(still a badarse character though >_>)