Hi, Mollina —
Good question for this time of year.
There are three oils. Only one of them is used in the Anointing of the Sick.
- OI = Oleum Infirmorum (Oil of the Sick)
- OC = Oleum Catechumenorum (Oil of the Catechumen)
- O-Chr = SC (more usual) = Sancta Chrisma (Sacred Chrism)
I am sure there is a lot of information on-line about the uses of these three oils which are blessed at the Chrism Mass each Holy Week.