Before we get to ninjutsu, taijutsu, or genjutsu, we must first discuss chakra

Chakra was first wielded by Kaguya, which is why she's called the mother of all chakra.

She obtained chakra by eating a fruit on a tree. (Lol)

Hagoromo and Hamura are the first people to be born with chakra, and while Hamura went to the moon to do whatever the fuck, Hagoromo stayed on earth and taught people how to use chakra to communicate in a practice called ninshu.

(Don't offend my man Hagoromo. He did not make ninjtusu. The man was abt peace)

[ WHAT IS CHAKRA ]

According to Navutu Dreams, the word Chakra is a Sanksrit word meaning “wheel” or “circle”, and it refers to the individual circular spinning wheels of energy located throughout the body. The Chakra System is a complex network of energy channels connecting these wheels and is mapped throughout the whole body, much like a spiritual nervous system. (Jan 11, 2017)

You can also define it as the combination of spiritual and physical energy.

Chakra is ordinarily not visible to the unaided eye unless it is highly concentrated or manifested in large amounts. This is rarely seen due to the restrictions of eight specific tenketsu known as the Eight Gates, (think of Gai sensei) which limit the amount of chakra an individual can release at a single given time. - Narutopedia

Everybody has a maximum amount chakra they can reserve or use, and they can push those maximums through training. However, genetics also play a role, so someone like Tenten cannot have the same chakra as someone like Naruto.

Chakra is used to create jutsu, yes, but it can also be used for general performance enhancement from strength to even mental functioning.

[ CHAKRA SIGNATURES ]

EVERYONE in Naruto has a different type of chakra that can be sensed by sensor type ninjas and seen by those with dojutsu (eye prowess).

Karin called Naruto's chakra bright and warm, and even sensed some evil chakra within him, meaning that to an extent chakra can relate to one's personality (it is spiritual energy)

Karin once stated that Sasuke's chakra began to get colder and more sinister, meaning that chakra can change as the person changes as well. She also couldn't recognize Kabuto's chakra when he had gone all snakey, because Kabuto had taken in a lot of other people's chakra therefore changing his chakra signature to a "nasty one" as Karin said.

Dojutsu users can see chakra, and chakra comes in different unique colours it seems.

Clans or families have similar but not exactly the same chakra signature.

[ THE CHAKRA PATHWAY SYSTEM ]

Think of it as a cardiovascular system, but instead of supplying blood to various organs in the body, it supplies chakra. Everyone in naruto has this system, but shinobi learnt to generate and excrete(lmao) this chakra through points called tenkutsu, which allows them to perform jutsu

[ HOW TO TRAIN CHAKRA ]

GENERALLY : chakra is trained through mental/spiritual ( studying, meditation, and experience) and physical processes (stimulants, training and exercise).

[ CHAKRA CONTROL]

The ability to control and conserve chakra is known as chakra control.

For example, if one puts too much chakra into a technique they will tire out quickly, but if one doesn't put enough chakra then the technique won't be performed efficiently or even at all. One needs to put in AN EXACT amount.

The basic chakra control trainings are Leaf Concentration, Tree climbing and water walking, which i will talk about in detail in another chapter.

According to narutopedia, a good way to build up chakra in the body is to spin it into a tight spiral; Whether to spin the chakra left or right is dependent on the way the user's hair grows. Hand seals are often used to manipulate chakra more easily, allowing shinobi to execute their techniques faster and more effectively. Shinobi who are extremely skilled at chakra control often specialise in genjutsu or become medical-nin.

[ REFERENCES ]

https://navutudreams.com/blog/chakras-explained-the-7-chakras-you-need-to-know-about/

https://naruto.fandom.com/wiki/Chakra