Slavery

Slavery is the act of owning other humans (as well as other sapient beings by extrapolation) as property. As slaves were bound to their owners they were prevented from leaving or refusing to work under threat of immediate violence for disobedience. This practice in one way or another has been fairly widespread in one way or another across numerous cultures throughout recorded history. When two groups fought, the victor would capture some of the defeated along with goods and put them to work. Latter on as long distance trade improved they also began selling said captives.

Customs and practices in regards to slavery varied from civilization from civilization based on a variety of factors. For many ancient civilizations slaves were fairly rare and were typicall and as domestic servants and/or concubines by the rich or doing a specific trade if they had a skill. The Greeks and especially the Romans managed to acquire made much more extensive use of slavery in a variety of fields, ranging from being worked to death in mines to high ranking government officials who lived more comfortable lives than most free citizens and everything in between. Occasionally slaves were used as soldiers (Ottoman Janissaries). Sometimes masters had absolute powers of life and death over their slaves while in other cases slaves had some minor legal protection. From the 16th to 19th century when the Europeans began to colonize the new world they made extensive use of slavery with a slave population imported from Africa, which led to develop the idea of Racial slavery (that black people were naturally suited to be slaves).

In addition to the practice of owning human beings as chattel there are other arrangements similar to slavery so that they are referred to as slavery informally. A few of these include Russian Serfdom (Serfs were not owned, but they were bound to the land owned by nobles and are required to work it), indentured servitude in colonial America (a guy has a debt to a master and has to work for him for a term of years and you will be punished for failing to do work during that term), the various forced labor programs used by the Nazis and the victims of human trafficking. Comparison to slavery is often used as a rhetorical device to describe bad working conditions or precised oppression.

Starting in the 19th century, slavery was gradually abolished. First by Britain in 1834 and latter by other powers, despite some disagreement from those in the Southeast of the US about the matter until 1865. Legal slavery does not exist, though human trafficking and illegal slavery remain a problem.

Slavery in Fantasy

Slavery is one of the token features of a setting's bad guy and an easy way to establish that a certain civilization is evil is that civilization making use of slaves. However, this is not always the case; both the perceived "good" and "bad" factions can also engage in slavery, although how they do it usually defines who's good and who's bad (regardless of how minute the difference is).

Take the Imperium and the Dark Eldar in 40K's setting, for example. Both factions engage in wanton slavery and have no qualms about it being a common thing everywhere. However, what sort of defines each of them is how they see their slaves. The Imperium sees their slaves as token currency to be spent for the good of the greater Imperium (for better or for worse), while the Dark Eldar mostly just sees them as playthings to torture to prolong their lives and also a form of currency in Commoragh....ok granted, both the Imperium and Dark Eldar are just fucked up asswipes.