The Chrism Mass, which [the Bishop] concelebrates with Priests from various regions of the diocese and during which he consecrates the sacred Chrism and blesses the other oils, is among the principal manifestations of the fullness of the Bishop’s Priesthood and is considered to be a sign of the close bond of the Priests with him. For it is with the sacred Chrism consecrated by the Bishop that the newly baptized are anointed and those to be confirmed are signed. It is with the Oil of Catechumens that catechumens are prepared and disposed for Baptism. Finally it is with the Oil of the Sick that those who are ill are comforted in their infirmity.
— The Order of Blessing the Oil of Catechumens and of the Sick and of Consecrating the Chrism (OBO), no. 1, taken from USCCB.org