Magic is defined as "the art or science of causing change to occur in conformity with will". Since humans are basically motivated by emotions of love and hate, magic has developed into two forms: one which is motivated to benefit mankind, commonly termed 'white' magic, and the one which is present to injure mankind, termed 'black' magic.
It is usually misconstrued that anyone who successfully practices magic is a witch. This is not true as magic in itself is a practice. Therefore, anyone may learn and use this art in their lives. Such a person is properly referred to as a 'magician'. A witch is a person who belongs to the old religion of pre-Christian Europe commonly called witchcraft, and often referred to as Wicca in today's times.
The type of magic that asserts your will over someone else in a strong, binding, and permanent way, or which is meant to cause damage, harm, or death is called black magic (for example, a spell to cause pain, damage property, exert control, or gain power over someone). These are the kinds of spells that sorcerers use. These purposes are highly unethical, and should be avoided by the Wizards.
The simplest form of black magic is sorcery, in which a certain physical act is performed to achieve a particular result. For example, a wax image is melted over a fire to kill a victim; blood is scattered over a field to ensure a bountiful harvest in the next growing season; knots are tied in a cord to store wind for a sea voyage, etc. Thus, sorcery forms the bulk of folk magic, and it's often popularly referred to as "Black Magic".
One of the reasons for the association of black color is that, much of this art originated in Egypt, called Khem, meaning "black" in ancient times. This is because the fertile flood-deposited soil of the Nile Delta was dark-colored, in contrast to the barren sands of the surrounding deserts, which were red. Therefore, in Egypt, black was good and red represented evil. Many Egyptians were dark-skinned, reinforcing the color association with their land.
It is the intention of the magician that determines the purpose and alignment, not the associated color. Black magic itself is not necessarily evil. Fundamentally, it is about power and control; power to do things, to control the world, and to dominate others. And just as weapons may be used either in aggression or defense, this form of magic is also the color of protection.
People talking about this art, generally refer to it as being used for selfish purposes rather than helpful ones. In particular, actions like dominating and manipulating people against their will, compelling people to do things they don't wish to do, working against the best interests of others, intentionally inflicting harm on others, threatening, oppressing, controlling, power-tripping, ripping off, etc., are all considered to be practices under the Dark Arts. True Wizards simply do not use magic in this way.
Another form of black magic is necromancy, in which the spirits of the dead are conjured up for consultation. This is what happens in a séance, where a medium goes into a trance, summoning and allowing spirits to temporarily inhabit his or her body, and simultaneously speaking. This is most often done at the request of a living relative, who might wish to question a departed soul regarding some important matter, or even seek reassurance that they are happy in the Afterlife.
Disclaimer: This article is for reference purposes only, and does not recommend any of the practices and actions mentioned above.