For Christians, Easter is the holiest and oldest of all traditions, and it's related to the even more ancient Jewish festival of Passover. Both holidays are celebrated at the same time of year, often (but not always) in the same week. Passover takes place over one week in remembrance of the exodus of the Jews from Egypt. For Christians, Easter commemorates the resurrection of Christ after his crucifixion.
In Austria, there's a unique event in the religious observance of Easter. Between Holy Thursday and Easter Sunday morning mass, you won't hear any church bells ringing, because according to religious lore, they all fly to Rome. Instead, the "Ratschenbuben" (altar boys with rattles) walk through the streets, making a lot of noise with their "Ratschen"(wooden rattles) saying prayers, and singing rhymes.