[Disclaimer: This is my first Holy Week celebration as a Catholic. Thus, so as to not have any misrepresentations below seem representative of the Catholic belief, I have entitled this "from the Perspective of a Catholic" instead of "from a Catholic Perspective.]
Today begins what we Catholics and other liturgical groups call the Paschal Triduum, which begins with the rememberance of the Last Supper. On Holy Thursday is the Mass of the Lord’s Supper at evening, followed by Good Friday, Holy Saturday, and Easter Sunday.
One week before Palm Sunday, all the images and the crucifix(es) are shrouded in purple linen. This signals a time of mourning as we draw near to Christ’s Passion. Palm Sunday is when we receive the palm branches, signifying the entrance of Christ in Jerusalem, which are blessed and become sacramentals (that is, they are set aside for a purpose to bring to one’s remembrance to do good). During Lent, the Gloria (“Glory to God in the highest and peace to His people on earth . . .”) is omitted.
When Holy Thursday comes, the focus is on the solemn celebration of the Last Supper, the institution of the Eucharist. The celebration also includes the institution of the priesthood. The Gloria is sung once again as every bell in the church rings. There is often a time of foot washing after the homily. The conclusion of the Mass takes places with the procession of the Blessed Sacrament from the main altar to another altar, the Altar of Repose, that is located in the chapel or in a room apart from the main altar. In our case, the Altar of Repose is in the parish hall.
After the procession, the altar(s) is stripped bare of all the linens and decorations. The altar is representative of Jesus, and this stripping of it represents the abandonment and stripping of Jesus. The candle that perpetually burns the rest of the year to indicate the presence of the Blessed Sacrament in the tabernacle is extinguished.
One word about the Blessed Sacrament. Catholics believe that during the consecration of the communion host the metaphysical properties of the bread is changed to the body of Christ. Thus, the bread communicates the real presence of Christ. One consecrated host is designated the Blessed Sacrament and it is kept in the tabernacle of the church to indicate that Christ is present. Because the Blessed Sacrament is metaphysically Christ’s body and communicates the real presence of Christ, Catholics give adoration to the Blessed Sacrament. When it is moved to the Altar of Repose, there is a time of adoration before the Blessed Sacrament before everything is locked up.
On a final note, in Catholic devotion, the usual rosary meditation for Thursday is the Luminous Mysteries (although this set of mysteries is only a few years new so it is not widely used). The popular rosary is a set of five meditations (which differ each day) on the life of Christ Jesus and of Mary while praying the Lord’s Prayer, imploring the intercession of the Blessed Virgin Mary, and praising God in the Doxology (“Glory be to the Father, and to the Son, and to the Holy Spirit . . .”). The last mystery is the Institution of the Eucharist and is fitting for Maundy Thursday.
Then comes the continuation of the Mass on Good Friday . . .