Chrism (or holy oil) is a consecrated oil used to anoint confirmandi in the Catholic sacrament of confirmation (or chrismation) and newly ordained priest receiving the Catholic sacrament of Holy Orders. It is also used in the consecration of objects such as churches, altars, patens, and chalices. It is usually olive oil (although other plant oils can be used in cases when olive oil is unavailable) and is scented with a sweet perfume, usually balsam. Under usual circumstances, chrism is consecrated by a bishop at the chrism Mass, which takes place on Holy Thursday or just before Easter.

External Link

http://www.newadvent.org/cathen/03696b.htm