Black magic or dark magic is a form of sorcery that draws on assumed malevolent powers. This type of magic would be invoked to kill, to steal, to injure, to cause misfortune or 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 (or rather, the effect itself is malevolent by causing death to insects, but as an indirect consequence of black magic, good sometimes results, in the form of less pests around, etc).
In fiction it refers to evil magic. In many video games, such as Final Fantasy, black magic is simply used to distinguish between healing/defensive spells (such as cure) and offensive/elemental spells (such as fire), and does not carry an inherent good or evil connotation.
Black and white magic
The opposite of black magic is 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 persons that maintain this opinion include those belonging to most branches of Christianity, Islam 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.
Gnostic Luciferian: Dark Magic and Dark Arts refer to work involving the estranged, twisted and forgotten aspects of nature and self. An evil intent is not necessarily present in the Dark Magician. The Dark Arts are also a set of methods for pursuing genuine self-knowledge and mental emancipation.
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 not the same 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 element(s) 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: Both black and white magic are forms of sorcery, but are completely different from the base up and are accomplished uniquely, even if they achieve similar effects. This stance is often presented in fiction. In such books, the two classes of magic-users are portrayed as being both ideologically and diametrically opposed. In The Lord of the Rings the elves find it strange that Humans and Hobbits can even use a single word, "magic", which refers to both - since the Elvish tongues regard them also linguisitically as completely separate and unrelated.
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. By this interpretation, even such spells commonly seen as good can be misused, so healing could be used to regenerate the body to the point of cancer, for instance