In our liturgy, we often use material things to help us to understand what we celebrate and hope to attain.
God, as it were allows us to use these material things - water, bread, wine, oil - to teach us that all of creation has become channels of grace, through the incarnation of Jesus.
St. Ignatius has taught us, that we have been created to praise, reverence, and serve God and everything else on the face of the earth has been created for us to help us attain the purpose of our existence.
Jesus did not hesitate to use bread and wine as a channel of grace for his continual presence with us. Anointing with blessed oil was part of the spiritual culture of the Jewish people: Cf. Ps. 23:4: "my head you have anointed with oil." Ps. 45:7 speaks of "the oil of gladness." In some cultures, oil is also used medically for healing.
Jesus himself was the Christ, the Messiah, the "Anointed One," so, of course, anointing with holy oil is a significant part of Baptism, Confirmation, Holy Orders and Anointing of the sick.
Given the importance of Anointing with sacred oil, it is not surprising that there is a special solemn liturgy consecrating it for use during the year. This liturgy is celebrated by the Bishop in union with the priests of the diocese. It is meaningful for lay Catholics to participate in this Mass. The liturgy is also a reminder of the priests' communion with their Bishop and thanksgiving for their anointing in Baptism and confirmation.