I went through past chapters and I realized that I didn't explain terms or abilities properly so I will leave a short description below explaining those that have appeared, and the list will be updated with those that will appear in the future:
Practitioner: the term for cultivators, people seeking immortality through absorbing a specific type of Qi (energy) from a cultivating formula and using it to strengthen their soul and body. The reason why I chose the term Practitioner is because of the literal meaning of cultivator: it means cultivating, growing something. In Chinese stories, cultivators work because they grow a seed within them or that's how it's usually described as. But in this story, certain aspects of cultivation have been discovered through the advancement of Science. For instance, there's no seed planting-like visualization in cultivation, rather it's described as a process, the process of absorbing energy, transforming it into another form of energy known as Spirit Power, then using that to strengthen the physical body, and the soul, so that it can hold more Spirit Power.
Spellcasting: a term for modern Magic, the ability to alter the very physics of the world through the manipulation of Psionic Aether. Different from Practitioners, Casters use the Psionic Aether surrounding them rather than the Spirit Power within them. In this aspect, they cannot strengthen themselves and 'level up' like Practitioners however, they have merits in the speed, strength, or versatility of their spells. A major disadvantage for Casters is their reliance on SEC devices. Without them, they wouldn't be able to formulate the necessary calculations needed for their spells. They are seen as Demi-Practitioners, simply because the would excel if they were to practice formulae. Unfortunately, Aether condenses into their spirit power, making it hard for them to become fluent Practitioners.
Espers: a curious mutation, or awakening, that occurred within humans after the cataclysmic disaster of the Meteor Incident. 35 years after the destruction of the moon and the meteorite shower that followed it, humans of any age began exerting abilities that could not be explained through conventional Science. They performed feats without the aid of a SEC, causing mass panic to ensure around the world as the World War was still in process. Eventually, a theory, based on Quantum Science, was formed, explaining that the Psionic Aether had somehow allowed people to alter the physics of the world without the aid of Aether. Simply put, the Espers had created a new world that focused around, and within, them that followed it's own set of rules, and was capable of altering the physical world around them based on a power level defined by the UN. What terrified many were the emergence of Espers among Casters, people with possibly double or triple the power of an ordinary Caster straight from the get-go and with the potential of becoming, even more, stronger in the future.
SEC Device: a computational machine that calculates the amount of Aether required and the calculation needed to transform it into the spell the Caster has made. It is also used to monitor Espers as well, telling them their level in power, their psychic gauge, and limiting their power if it exceeds the minimum safety of the wearer's health. Usually, a single SEC is enough to handle an Esper or Caster's ability however, it is not unknown for powerful individuals to wear more than one SEC Device.