Black magic or dark magic is type of magic that draws on malevolent powers. It is used for malevolent acts or to deliberately cause harm in some way. It is alternatively spelt with a 'K' (magick), this term is also known as black magick, dark magick, the dark arts of magick and dark side magick.
In modern times, people who believe in or claim to practice magic use the term to describe the harmful magic that they consider taboo, as opposed to the good white magic that they do profess to practice.
Black magic would be invoked to kill, injure, or cause destruction, or for personal gain without regard to harmful consequences to others. As a term, "black magic" is normally used to describe a form of ritual that some group or person does not approve of. Not everything that is called black magic truly has malevolent intentions behind it, and some also consider it to have beneficial and benevolent uses, such as killing off diseases or pests.
Magic like this is used to directly harm one's opponent in role playing games like Final Fantasy, for example. The opposite of dark magic is white magic. Since the words "black magic" have a negative connotation in American TV-Y rated TV shows, this phrase is used instead of "black magic" on Magical DoReMi.
Black and White Magic
The differences between black magic and white magic are debatable, but theories generally fall within the following broad categories:
All as One: All forms of magic are evil, or black, magic. This view generally associates black magic with Satanism. The religions that maintain this opinion include most branches of Christianity, Islam, Judaism, and Hinduism. Some people on the left-hand path would agree that all magic, whether called "white" or "black," is the same. These people would not contend that all magic is evil so much as that morality is in the eyes of the beholder - that any magic can have both good and bad consequences depending on who judges those consequences. In this school of thought, there is no separation between benevolent and malevolent magic because there is no universal morality against which magic can be measured.
Dark Doctrine: Black magic refers to the powers of darkness, usually seen from a Left-Hand Path point of view. This may or may not contrast with White magic, depending on the sorcerer's acceptance of dualism.
Formal Differences: The forms and components of black magic are different, due to the different aims or interests of those casting harmful spells, than those of white. Harmful spellcasting tends to include symbolism which seems hazardous or harmful to human beings, such as sharp, pointed, prickly, caustic, and hot elements combined with very personal objects from the spell's target (their hair, blood, mementos, etc.). This distinction is primarily observable in folk magic, but pertains to other types of magic also.
No Connection: Black and white magic are both forms of magic, but are completely different from the base up and are accomplished differently, even if they achieve similar effects. This stance is the one most often presented in fiction, including the Harry Potter series. In such books, the two classes of magic-users are portrayed as being both ideologically and diametrically opposed.
Separate but Equal: Black and white magic are exactly the same thing, differentiated only by their end goals and intent. According to this theory, the same spell could be either white or black; its nature is determined by the end result of the spell. The majority of religions follow this belief, as does the remainder of fiction that does not follow the No Connection theory.