The First Sunday of Lent

This is the first Sunday of Lent. In the Eastern [Byzantine] Catholic Churches the First Sunday of Lent is known as the Sunday of Orthodoxy. [It] commemorates the Triumph of Orthodoxy: that is, the victory of the True Christian Faith over heresies and enemies. The First Sunday of Great Lent celebrates the victories of the true Christian faith over heretics and other adversaries.

On the First Sunday of Great Lent, we traditionally have a procession with the holy ikons at the end of the Divine Liturgy, and all the ikons are held for veneration by all the people.

The reason for the procession with the holy ikons is that this Sunday especially celebrates the restoration of the ikons and other holy images to Christian worship after the defeat of the Iconoclastic heresy (heresy of Iconoclasm) of the 8th and 9th Centuries. (In Greek, the word "Iconoclast" means "image smasher".) Iconoclasm opposed the use of ikons, statues, and all images of Holy God the Son within the Holy Trinity / Our Lord, God, and Savior Jesus Christ and the saints. Many ikons were removed from churches and homes and were destroyed. In 843, under the Empress Theodora, there was the final restoration of the holy ikons. This action was know as the Triumph of Orthodoxy and is celebrated on the Sunday of Orthodoxy.

There is more at this Melkite site. (Not all Eastern Churches use the Gregorian calendar and the Roman method of calculating Easter. Most in the United States seem to, though, and they observe the First Sunday of Lent at the same time as the Western Church. For those who do not, it will usually be some weeks later.)