A harem is usually a group of women which lived under a household and were forbidden to any other men other than the caliph. It was introduced by the Abbasid court during the Islam Empire, as the veil was being introduced as well. The women naturally had sexual relations with the caliph, and gave birth to his children, whom lived with them in this harem, and were prohibited to leave the quarters of the Imperial palace. Most concubines were slaves, who won their freedom by bearing healthy sons for the rulers.