Spellcasters are those magical creatures whose only magical ability is that of casting spells, otherwise known as Spellcasting. Spellcasters are very powerful but can found themselves powerless without their channeling tools, which is usually a wand.
Types of Spellcasters
The Angels, both Guardian and of Darkness, seem to possess enough raw magic to be able to cast spells and incantations. Though, however, they seem to not be very skilled at it. Rosie was capable of casting spells correctly when she was enchanted by Alex to do so, while Gorog, supposedly more powerful than Rosie, needed Felix to cast spells (though due to Felix's ownership of the Wizards World's most powerful wand, Felix's spells are more powerful than those of ordinary spellcasters).
Elves are very powerful magical beings that appear to have the power of casting spells, as was the case of Tutor. However, Tutor was a half-elf and it's not known if one of her parents was a Wizard. Assuming elves are natural spellcasters, it's unknown if they need wands as Wizards do or if they have to pay a Power Bill for their powers being sustained by the Wizard Power Plant.
Fairies are winged spellcasters that wield a magic wand to cast powerful spells. Most likely fairies powers have the same limitations and ranches of those of Wizards. Fairies also seem to be capable of manipulating their size and fly around without the need of a wand.
Wizards magic is centered in casting spells and they seem to have as Justin says "a spell for everything minus how to undo a mutant spell". Wizards use their spells to cause effects of powers that they don't have, such as telekinesis, invisibility and cloning, which seem to be never lasting. Also, Wizards can teleport away without the need of wands (though it seems to be just low-range limitation).
In Disenchanted Evenning, when Justin, Alex and Max teleport to Mars they were being watched by local Martians. When they left, one of the Martians said that he had enough information about wizards from Earth. This gives the impression that wizards might also exist in other non-earth races.