On Holy Thursday, Catholics commemorate the institution of three pillars of the Catholic Faith: the Sacrament of Holy Communion, the priesthood, and the Mass. During the Last Supper, Christ blessed the bread and wine with the very words that Catholic priests use today to consecrate the Body and Blood of Christ during the Mass and the Divine Liturgy.
At Mass on Holy Thursday is also customary for the priest to wash the feet of twelve parishioners to symbolize Christ's washing the feet of his Apostles.