A host is a thin, round wafer made from bread and used for Holy Communion in many Christian churches. The word is from the Latin, "hostia", which means "victim" or "sacrificial animal." The term can be used to the bread both before and after consecration, though it is more correct to use it after consecration - "altar bread" being preferred before consecration.In the Roman Catholic Church, hosts are often made by nuns as a means of supporting themselves. It is required that the hosts be made from wheat flour and water only (Code of Canon Law, Canon 924). The Roman Church teaches that at the words of consecration the bread is changed into the Body of Christ through transubstantiation.
See more at Wikipedia.org...