"Since the revision of the Catholic liturgical calendar in 1969, Passiontide has been synonymous with Holy Week. Palm Sunday, the final Sunday before Easter, is now known as Passion Sunday, though in practice it is almost always referred to by its former name. (Sometimes you may see it listed as Passion (Palm) Sunday, reflecting the current usage.)
Before the revision of the liturgical calendar,
however, Passiontide was the period of Lent that commemorates the increasing revelation of Christ's divinity (see John 8:46-59) and His movement toward Jerusalem. Holy Week was the second week of Passiontide, which began with the Fifth Sunday in Lent, which was known as Passion Sunday. (The Fifth Week of Lent was likewise known as Passion Week.) Thus Passion Sunday and Palm Sunday were (unlike today) separate celebrations.
The revised calendar is used in the Ordinary Form of the Mass (the Novus Ordo), which is the form of the Mass celebrated in most parishes. The Extraordinary Form of the Mass (the Traditional Latin Mass) still uses the previous calendar, and thus celebrates two weeks of Passiontide.
In both the Ordinary and the Extraordinary Forms of the Mass, Passiontide is observed with great solemnity, especially because Passiontide includes the Triduum, the final three days before Easter. Under the older, two-week Passiontide, all statues in the church were veiled in purple on Passion
Sunday and remained covered until the Easter Vigil on Holy Saturday night. The practice still largely survives in the Novus Ordo, though different parishes observe it differently. Some veil their statues on Palm Sunday; others, before the Mass of the Lord's Supper on Holy Thursday; still others remove the statues from the church altogether and return them to the church for the Easter Vigil."