Wizards
Everyone in Ozel has the capacity for magic. However, that's like saying everyone IRL has the potential to become a nuclear physicist. Whereas other, more innate types of casters are content with a smaller array of spells that come to them, Wizards devote their time to studying theory and application, thus affording them a wider list of spells to learn. New spells get created all the time, however when it comes to adventuring and warfare, practicality is king. Thus, spells that require hard-to-find resources or aren't worth the energy put in don't often get included in the curriculum.
Warlocks
Warlocks in Ozel are treated with suspicion, but only tend to risk persecution in more remote areas that breed superstitions. That being said, the determining factor in how a Warlock is treated depends on their patron. Fiendish warlocks are viewed with skepticism or pity, for the caster is inevitably going to serve as a catalyst for some nefarious purpose, and pay the price once they die. Deities related to Death are typically said to bring them to a sort-of purgatory, collectively known as Limbo, Shadowfel, or simply "Between." There it is determined whether the pactmaker's soul is bound for Avernus, or is somehow spared that fate. Fey warlocks, on the other hand, are treated with extreme caution. Typically they seem harmless enough, looking as if they worked in the glue factory too long. But Fey are mischievous and chaotic, and one can never be too careful when they are involved. The core of what makes a Warlock is that the patron has bestowed upon them a power in exchange, explicitly, for service.
Sorcerers
As opposed to studying or being given power, Sorcerers inherited certain magical abilities through their ancestors. Scholars are still trying to work out the exact mechanisms, for a sorcerer parent may not necessarily give birth to a sorcerer child. However, that child could end up with a sorcerer child of their own one day. It comes and goes, with no real pattern or reason. Usually the ancestry is concrete; a dragon, a wizard who dabbled in wild experiments, so on so forth. The more obscure ones, such as Shadow or Divine, tend to be considered harder to track down. Rather than suggest that a parent was somehow a Celestial or Averni, it's figured that the ancestor in question may have been a Warlock, and the pact magic somehow got transferred to the fetus during pregnancy. This, however, is unconfirmed and research is ongoing.
Druids and Rangers
No matter what religion, the obscurity and power of nature is well known. Nature has a way of being both orderly and chaotic, but somehow maintaining a very precarious balance. Theories point to this balance as being the catalyst for giving druids and rangers their spellcasting abilities. To commune and utilize nature's energy is to understand this balance and strive to keep it from swaying one way or another.
Clerics and Paladins
Like Warlocks, Clerics and Paladins earn their power through service. However, this is more of an implicit exchange, as it is through reverence and carrying out a God's will that gives them their strength. The God (usually) does not give their worshipers explicit instructions, only guidelines to follow, and that is enough to satisfy them. While most tend to follow a single God or code, it is not uncommon for clerics to request the aid of another God, and temporarily be granted their strength, albeit in a much lesser capacity.
Witches
Often lengthened to "Witch of the Wilds" due to their propensity to live as hermits in the woods. Witches are those that practice any of the above forms of magic, but tend to be morally gray in their applications. They dabble in spells that tend to err on the forbidden side, though this does not necessarily mean they are bad. Rather, the magic that witches often use simply tend to cost greater than ordinary spells. Potions, rituals, and exchanges are their trade. More malevolent witches, or "hags," tend to use their magic on others for their own gain, often with the recipient being harmed in some way. More benevolent witches, or "white witches," tend to provide sources of unorthodox healing, though the efficacy is questionable. Many serve as doulas, caregivers who assist in midwifery or end-of-life care.
Other
Magic is by its own very nature unpredictable. There have been cases of people able to cast a spell during times of great need, but never again. A community does not need a cleric to collectively satisfy a God's needs and be granted prosperity. And, most strangely, there are those who at some point in their lives develop a strange brand or marking. The cause could be any number of things, but what is known is that power is often granted to them (though limited compared to Warlocks), but for an unknown purpose. These "Anomalies" as they are known are suggested to keep their marks hidden. A Fiend Warlock, at least, can be sure to do something to benefit an Averni. A Cleric of a certain God will be sure to do acts that benefits their respective dominion. However, the Unknown is often what inspires the most fear.