The Catholic Church uses three holy oils: Sacred Chrism, Oil of Catechumens, and Oil of the Sick. These oils are blessed or consecrated by the Bishop during the Chrism Mass. 
If you're an altar server or sacristan -- or even a deacon of priest -- the various oils may still be confusing. I know it's been a tough one for me. 



Here's the breakdown:Sacred ChrismSC for Sanctum Chrisma Sacraments: used for the Sacrament of Confirmation and Baptism   Ingredients: made from olive oil and balsam Oil of CatechumensOC for Oleum Catechumenorum, also OS for Oleum Sanctum, also "Oil of Exorcism" - at our Church, I'm pretty sure the canister says OC and the cruet says OS, so heads up! Sacraments: only used for the pre-Baptized, the pre-Baptized are called "catechumens" (pl. catechumenate)Ingredients: made from olive oil only  Oil of the SickOI for Oleum Infirmorum, also called Oil of Healing Sacrament: used in the Anointing of SickIngredients: made from olive oil only
Does this help? Does this resolve all the confusion? Please let me know if you have any more questions!