Magic is the power to use spells to cause supernatural alterations in the world. Magic is used by various characters to wield supernatural powers which can be used for both good or evil. Some practitioners of magic such as sorcerers and witches use their power for evil though not all do that.
Magic can be used through magic wands or by being inherently magical, such as in the case of genies or dragons. Those beings can cause magical alterations by sheer will. Sorcerers have to study spellbooks and other books of witchcraft to obtain and control their powers.