Of Holy Week in general

45. Because the last week of Lent is called holy?
The last week of Lent is called holy, because in it the memory of the greatest mysteries brought about by Jesus Christ for our redemption is celebrated.
46. What mystery is remembered on Palm Sunday?
On Palm Sunday we commemorate the triumphant entry that Jesus Christ made into Jerusalem six days before his passion.
47. For what reason did Jesus Christ enter triumphantly into Jerusalem before his passion??
Before his passion, Jesus Christ wanted to enter Jerusalem triumphantly, as had been predicted:
1. to animate his disciples, thus giving them clear proof that he was going to suffer spontaneously;
2. to teach us that with his death he would triumph over the devil, of the world and of the flesh, and that it would open the entrance to heaven for us.
48. What mystery is celebrated on Holy Thursday?
On Maundy Thursday the institution of the Holy Sacrament of the Eucharist is celebrated.
49. What mystery is remembered on Good Friday?
On Good Friday we remember the passion and death of the Savior.
50. Which mysteries are honored on Holy Saturday?
On Holy Saturday the burial of Jesus Christ and his descent into limbo are honored and after the sign of the Gloria we begin to honor his glorious resurrection.
51. What must we do to spend Holy Week according to the mind of the Church?
To spend Holy Week according to the mind of the Church we must do three things:
1. combine fasting with greater internal concentration, and a greater fervor in prayer;
2. meditate continually with a spirit of compunction on the sufferings of Jesus Christ;
3. assist if you can, to the divine offices with this same spirit.

Of some rites of Holy Week

52. Because the Sunday of Holy Week is called Palm Sunday?
The Sunday of Holy Week is called Palm Sunday because of the procession that takes place on this day, in which the faithful carry an olive or palm branch in their hands.
53. Because on Palm Sunday there is a procession carrying olive branches or palms?
On Palm Sunday there is a procession carrying olive or palm branches to remember the triumphant entry of Jesus Christ into Jerusalem, met by the crowds with palm branches in their hands.
54. Because on the return of the Palm Procession the door of the Church is knocked three times before it opens?
On the return of the Palm Procession, the door of the Church is knocked three times, before it opens, to mean that paradise was closed due to Adam's sin, and that Jesus Christ deserved entry with his death.
55. Who were those who met Jesus Christ when he entered Jerusalem triumphantly?
When Jesus Christ entered Jerusalem triumphantly, the simple people and the children went to meet him, not the big ones of the city; thus disposing God to make us know that pride made these unworthy of having a part in the triumph of our Lord, who loves simplicity of heart, humility and innocence.
56. Because the bells are not rung from Holy Thursday to Holy Saturday?
From Thursday until Holy Saturday the bells are not rung as a sign of great affliction for the passion and death of the Savior.
57. Because a large consecrated host is preserved on Holy Thursday?
On Holy Thursday a large consecrated host is preserved:
1. so that special adorations are paid to the sacrament of the Eucharist on the day it was instituted;
2. so that the liturgy can be performed on Good Friday, in which the consecration is not carried out by the priest.
58. Because on Holy Thursday after Mass the altars are stripped?
On Holy Thursday after Mass the altars are stripped to represent Jesus Christ stripped of his clothes to be flagellated and affixed to the cross; and to teach us that to worthily celebrate his passion we must strip ourselves of the old man, that is, of every worldly affection.
59. Why feet are washed on Holy Thursday?
On Holy Thursday, feet are washed:
1. to renew the memory of that act of humiliation with which Jesus Christ stooped to wash his Apostles;
2. because He Himself exhorted the Apostles and, in person of them, the faithful to imitate his example;
3. to teach us, that we must purify our hearts from every stain, and exercise towards each other the duties of Christian charity and humility.
60. Because on Maundy Thursday the faithful go to visit the Blessed Sacrament in several churches publicly in processions, or privately?
On Holy Thursday the faithful go to visit the Blessed Sacrament in several churches in memory of the pain suffered by Jesus Christ in several places, like in the garden, in the houses of Caiaphas, of Pilate and Herod, and on Calvary.
61. In what spirit should visits be made on Holy Thursday??
On Holy Thursday visits must be made not out of curiosity, out of habit or for fun, but out of sincere contrition for our sins, which are the true cause of the passion and death of our Redeemer, and with a true spirit of compassion for his sufferings, meditating on the various sufferings; for example in the first visit what you suffer in the garden; in the second, what he suffered in Pilate's praetorium; and the same goes for the others.
62. Because on Good Friday the Church, in a particular way, pray to the Lord for all sorts of people, also for the pagans and for the Jews?
The Church on Good Friday, in a particular way, pray to the Lord for all sorts of people to demonstrate that Christ died for all men and to implore the fruit of his passion for the benefit of all.
63. Because on Good Friday the cross is solemnly adored?
On Good Friday the Cross is solemnly adored, because Jesus Christ was nailed there and died there on that day, he sanctified it with his blood.
64. Worship is due to God alone, because therefore the Cross is adored?
One owes worship to God alone, and therefore when the Cross is adored, our worship refers to Jesus Christ who died on it.
65. This is something to be considered especially in the rites of Holy Saturday?
In the rites of Holy Saturday, the blessing of the Paschal candle and the baptismal font must be especially considered.
66. What does the Paschal candle mean?
The Paschal candle signifies splendor and glory, that the resurrected Jesus Christ brought to the world.
67. Because the baptismal font is blessed on Holy Saturday?
On Holy Saturday the baptismal font is blessed, because anciently on this day, as again on the eve of Pentecost, Baptism was solemnly conferred.
68. What should we do while blessing the baptismal font?
While the baptismal font is blessed, we must thank the Lord for having admitted us to Baptism, and renew the promises we made then.
source – Major Catechism of Saint Pius