The mystagogy of the celebration
In the liturgy of the Eastern Churches, the post-baptismal anointing is the sacrament of Chrismation (Confirmation). In the Roman liturgy the post-baptismal anointing announces a second anointing with sacred chrism to be conferred later by the bishop Confirmation, which will as it were "confirm" and complete the baptismal anointing.
Source: Catechism of the Catholic Church (Vatican.va)