Catharism was a complicated mix of non-Christian religions reworked with Christian terminology. The Cathars had many different sects; they had in common a teaching that the world was created by an evil deity (so matter was evil) and we must worship the good deity instead.
The Albigensians formed one of the largest Cathar sects. They taught that the spirit was created by God, and was good, while the body was created by an evil god, and the spirit must be freed from the body. Having children was one of the greatest evils, since it entailed imprisoning another "spirit" in flesh. Logically, marriage was forbidden, though fornication was permitted. Tremendous fasts and severe mortifications of all kinds were practiced, and their leaders went about in voluntary poverty.