Holy Thursday begins the Easter Triduum–the three days leading up to Jesus’ Resurrection. Its formal name is Mass of the Lord’s Supper, which was the first celebration of the Eucharist.
This liturgy includes the reception of the Holy Oils, in which the Oil of the Sick, the Oil of Catechumens, and the Holy Chrism are processed through the church, to be used for the rest of the year. These oils are all blessed by the local bishop shortly before the liturgy during the Chrism Mass.
Also notable at the Holy Thursday service is the washing of the feet, in which the priest washes the feet of 12 parishioners. Jesus did this to demonstrate to his disciples how they are to serve others through selfless love.
Originally, only men were invited to be among the 12 to have their feet washed. A decree from Pope Francis in 2016 opened up the ritual to all.
At the end of Mass, consecrated hosts remain on the altar while everything else is stripped away. As incense fills the church, the priest, donning a special garb called a humeral veil, takes the Blessed Sacrament and processes out of the church to a chapel or other area for adoration.