Easter is the Church’s celebration of the resurrection of Jesus from His death on the cross. The liturgical season starts in the Easter Vigil (called the “Mother of All Vigils”) celebrated on the eve of Easter Sunday. This marks the end of the Holy Week and the last day of the Paschal Triduum. It is the most important celebration in the Church’s liturgical calendar, thus calling Easter Sunday the greatest of all Sundays.
In the Gospels, on the third day after His Crucifixion and death, Jesus Christ rose from the dead. His resurrection signifies His triumph over death, His victory against evil, and man’s salvation from sin fulfilling God’s promises to mankind.
Easter is simply derived from the word “East”. As the sun rises in this direction bringing the light of a new day that signifies risen Christ – the Light of the World. The Paschal Candle used during the Easter Vigil symbolizes the divine light of Christ. Throughout the season of Easter, this candle is lit on the altar for all liturgical celebrations. During this season, the faithful celebrate the resurrection of Jesus, His ascension to the Father, and the sending of the Holy Spirit upon the Church.
It is believed that Easter was celebrated regularly by early Christians. The date of Easter Sunday always falls on the Sunday following the first full moon after the spring equinox. The season of Easter spans seven weeks and ends on the day of Pentecost.
Easter Sunday: https://www.catholic.org/lent/easter.php
What is Easter? https://www.usccb.org/prayer-worship/liturgical-year/easter