“Icon” means “image” in Greek. It is the same Greek word used in Genesis 1 (“Humans are made in the image [eikon] of God”) and in Colossians by St. Paul when he speaks of Jesus as being the “image [eikon] of the invisible God.”
My definition of “Icon” in the sense of a holy painting is “a sacred traditional Christian image used for prayer and worship.” This brings in elements essential to understanding the nature of icons—that they are actually sacramental, like Baptism or Communion; that they are deeply traditional, with roots going back to the origins of Christianity; and that they are made for only one purpose: to help guide people to God in prayer and worship.
Icons are also an especially powerful way to illustrate the Incarnation. Because God became human in Christ, we may paint His likeness to help us remember His love for us.
Icons have been revered throughout most of the church’s history because they honor in a physical way the physical incarnation of God in Christ.
Following the fierce debate about icons in the previous decades—if they were indeed forbidden “graven images”—in 787 AD the church gathered in full ecumenical council to decide once and for all what icons were and what they were not. The council’s most important conclusion was that such pictorial representations are useful “so the incarnation of the Word of God is shown forth as real and not merely fantastic.”
If an icon is a vehicle for prayer and worship, then “the honor which is paid to the image passes on to that which the image represents, and whoever reveres the image reveres in it the subject represented.” But the council also clearly stated that icons are not idols and are not themselves to be worshiped.
In the following centuries icons were associated primarily with what became known as the Orthodox tradition, more formally so once the church divided between west (Rome) and east (Constantinople and later Moscow) in the 11th century. More recently the western churches have experienced a revival of interest in icons, recognizing them as part of the common heritage of the church universal.
Icons are doors for the mind as well as the soul and are sometimes called “theology in color”; they are meant to be “read” for the symbolic meanings contained in the elements of the picture. In fact, icons share a symbolic language of imagery and color that helps to draw our whole being into the presence of the divine. As the church observed in its 8th-century council, “the more often we see such icons, the more we are led to recall those depicted with love.”