Nice, you hit a couple of points there that I wanted to address..
for a better understanding I have a written out my own explanation on both Chakra & Ninjutsu. Let me know if you have any questions after.
Chakra:
You should also know that Chakra is comprised of both Spiritual & Physical energy of a living being, whether that being be human or animal, all creatures have a chakra network than runs through their system. Spiritual energy is thought of as being related to the being's mind & spirit, I would like to think that the more a living being is in tune with their mind & spirit, the more control they have over their own chakra, leading me to believe this is how one would gain a mastery over their "Chakra Control" a title used in many aspects of the Narutoverse. Physical energy is related to a being's body & vitality, something that can also be seen as one's inner strength & "Will". A life force with a greater physical energy would usually have a large source of chakra.
Chakra itself does not require to have an equal amount of both Physical & Spiritual energy. As noted some beings have a greater source of physical energy while others a spiritual. An example of a large source of physical energy would be the Uzumaki, a clan that is named for having large sources of chakra due to an extended life force. An example of spiritual energy would be the Uchiha, their Sharingan has a closer relation to spiritual energy rather than physical. This allows a Uchiha member to gain a visual prowess over such others like Senju or Uzumaki.
Ninjutsu:
Ninjutsu is a skill that allows one to control & manipulate their chakra, resulting in them creating a desired technique. There are two main portions of ninjutsu that are used to "enhance" a technique, these are known as Shape manipulation & Nature transformation. Shape manipulation gains the user the ability to alter the form of a given technique, allowing them to create a desire shape to an already existing chakra source of their own, this can allow the technique to gain a different effect than it's original form. Nature transformation is the basis of elemental chakra (the basic 5 elements being the most common used & in some ways the "pillars" to creating advanced nature types), something which consists of altering chakra's nature to gain a set of characteristics & properties.
Handseal are hand gestures commonly used to better manipulate/mold a user's chakra. it usually aids with techniques that would require more concentration, & gain an improved control over a technique.