In-universe, magic is a broad term with several definitions, though all refer to supernatural phenomena of some kind. Outside of it, it can be described as any supernatural power or ability gained through summoning, bargaining, extorting, or making a deal with a non-living spirit.
Cultural perspectives of magic vary wildly. In the theocracy of Zantium, magic was seen as an exclusively evil and impure practice. It was termed witchcraft, a perversion of the national religion. The motivation of a person who uses magic - which, for the Zantines, could only be obtained through dealings with devils - was to obtain an extreme form of power over others, and thus it was a threat to society. The only way to counteract the power of magic was through exorcism of the spirits involved, or by slaying the magic user. Specially trained knights, called paladins, were taught how to fight against mages and spirits using special weapons. Any individual found to be using magic was put to death, although as the years wore on this was softened in favor of banishment or imprisonment.
Many of those sent into exile moved to the neighboring country of Iskirra, where they learned how to create enchanted items by binding their magic to steel. This led to a fusion of technology and magic which gave Iskirra mastery over the region, and enabled the Iskirrans to conquer Zantium.
On the other side, the desert land of Nykara is a tolerant/lenient society where all practices are tolerated. Magic is equated with religion, and thus it is protected under religious freedoms. This has led to some rather interesting conflicts as paladins who survived the destruction of Zantium and witches/warlocks who settled in Nykara rather than Iskirra are forced to live together even as their ideologies clash.