Palm Sunday traditionally has two focal points. One is the entrance of Jesus into Jerusalem just days before his arrest, trial and crucifixion. He was greeted with acclaim by residents, who placed branches of palm trees in his path, a sign of respect for an arriving messiah. Within a week, of course, the people of Jerusalem were making a different cry: “Crucify him!”
The other focal point is the reading of the Passion Gospel, the entire story of Jesus' final hours, beginning with his torment in the Garden of Gethsemane and concluding with his death on the cross and the placing of his body in a tomb. Thus the day usually is known as the Sunday of the Passion: Palm Sunday.
In many churches, the liturgy for that begins with an enactment of the procession into Jerusalem, with palm branches waved by worshipers. (Some of those branches will be saved until next year and then burned for use as the ashes on Ash Wednesday.) The Gospel reading for the day is the Passion Gospel, sometimes in a dramatic reading by several readers, with the congregation taking the part of the Jerusalem mob.
Many consider this the most moving liturgy of the year. Its relevance is both to tell the story of “Christ crucified,” as Paul put it, without which the story of Easter has no meaning; and to call attention to our complicity in turning against Jesus.