Magic

Aether is an energy that flows through everything. From forming patterns between the stars, to flowing in the very veins of every creature that inhabits the world, it is everywhere.
This aether can be directed and channeled into spells. Many people use glyphs, symbols with various meanings that give a sort of instructions for a spell. Writing out glyphs and channeling aether into them will cause the spell to be cast.
Glyphs are derived from constellations, as well as the hidden patterns in aether. There are a variety of glyphs, ranging from vague concepts like "wisdom" and "healing" to specific materials and objects like "mountain" and "water."
However, glyphs are not necessary for magic. Many people are able to cast spells by simply directing the aether on their own, without the use of writing glyphs. Typically, the trade-off is that these people are skilled in specific uses of magic, while using glyphs can make it easier to learn a wide array of spells.
While glyphs are traditionally used in magic, no style of casting is better than any other. Magic users cast spells in a way that feels right and works for them - there is no one right way to do magic.
The ability to cast spells is theoretically available to anyone. However, many people have much more of a natural talent. It is also dependent on the amount of practice and skill - no one can cast spells without any learning or training, although some learn more quickly than others.
When ambient aether is pulled out of the surrounding area to be used in a spell, the supply refills quickly. It is unclear if the essence is being recycled or if it is being used up and new aether is taking its place - which begs the question of where aether comes from. It is theorized by some that aether originates from the astral plane, although sufficient proof is still not able to be obtained.