It's a solemn time for Christians; our minds are on the sacrifice of Christ on the Cross before we can celebrate His resurrection.
Here's a very brief explanation of the days of Holy Week.
Palm Sunday is the celebration of Christ's entry into Jerusalem on an ass. In the Biblical story, people who witnessed the entry spread palm branches on the road to make the path soft for Christ as he rode. That's why at Palm Sunday Mass, blessed palm branches are distributed. Many people tie them into crosses (as my mother-in-law does). Last year and this year, I picked up a few extra after Mass and made a St. Brigid's Cross with them.
Holy Thursday is remembered as the day of the Last Supper with the disciples. Only hours later, Jesus was betrayed by Judas. This day commemorates Holy Communion, and usually ends with the emptying of the tabernacle in the main part of the church. The consecrated host that's moved to another place overnight is distributed on Good Friday. After the service, the altar is stripped, and any bells that are normally used are kept silent until Easter Vigil.
Good Friday, a day of fasting and abstinence, commemorates the Passion and death of Jesus. A full Mass is not celebrated. Instead, it's more of a memorial service that includes a reading of the Passion of the Lord, prayers are offered, and Holy Communion is distributed.
Holy Saturday commemorates the day Christ laid in the tomb after the Crucifixion. On this day, Holy Communion is only given to the dying, Masses are forbidden, and the altar remains stripped.
Easter Sunday is the celebration of the resurrection of Christ from the dead. Where Lent has been a somber time for reflection and introspection, Easter is a celebration. Usually, the music is joyous, the faithful can once again say and sing "Alleluia," and we celebrate the great gift Christ gave us by His Sacrifice. And afterward, we all go home to have delicious food and let our children gorge themselves on the chocolate they've probably been denied for their Lenten sacrifices.
This is a serious time for Christians. As we look ahead to Good Friday and Holy Saturday, we can't help but think of the pain Christ went through for our sake. But that pain culminates with a great gift, and one that is celebrated joyously.