There are many types of magic in the world, only a few are very well documented.
Basically sorcery consists of drawing on a source of energy and directing and shaping it. What this source of energy is exactly is unclear, it's pretty well known that it is extradimensional however. It's often called simply 'The source' or 'The Ocean' some believe it's an ocean of energy on some other world, others believe it's some kind of god.
Opening a way to this energy allows it to flood through, opening the way further, it can then be transformed into other forms of energy and directed as the wielder wishes.
Learning to do this is basically a type of meditation but it is not something that is commonly learned spontaneously. Without a teacher probably only one person in every two or three generations would discover the ability on their own.
Most people can be taught sorcery, but not all learn it as quickly or to the same level of proficiency what determines this is not well known, but it
Certain crystals and metal constructs can be patterned by using sorcery in order to act as batteries for spells or even under some conditions to perform spells themselves.
Rituals are a type of magic that can be performed by almost anyone. All
they require is access to the proper instructions which every faction library should have. They also require specific ingredients however, in particular they require human blood.
It's believed that rituals function by draining a form of energy from this blood, which is then fed through the ritual to spirits who carry out the request. Exactly what these spirits are or where they come from is unclear.
Gate Magic is another type of ritual, and again anyone with access to a faction library should be able to perform it. However it doesn't invoke spirits or take blood, rather it draws power from the Gate to enact it's effects, most usually those effects are related to the Gate itself, such as opening bridges to other worlds. A benevolent practitioner could use it to end a drought through making a bridge to the plane of water, while a malicious one could flood the world with a similar bridge. Luckily gate magic takes some time to perform and is usually detectable by seers so it's unlikely anybody could end the world without people noticing and trying to stop them.
Fleshforming is the oldest form of magic, it is nearly impossible to cast it without the help of a True Demon, Fae, God, or one of the reality terrors that are trapped in the Void. Fleshforming has allowed the Gods and Fae to give themselves ageless and invincible bodies, it allows all the primal supernaturals the ability to transform themselves, the world around them, and others. Native supernaturals of our world who've practiced fleshforming fail at it tremendously, often creating horrors or transforming themselves into nightmare creatures.