Iconography is a Greek word that literally means "image to write." Many religious paintings use scenes and symbols that can be "read," regardless of artistic style, to mean specific things. Because images so effectively convey meaning to a wide variety of people, Catholic art has a long history of employing complex iconographical symbols for a didactic purpose.

Life Cycle of Jesus

The life of Jesus is a major concern in Christian art, and is readily found in Catholic churches. There are hundreds of traditional scenes describing the life of Jesus, some of which are more recognizable to the modern eye than others. The most famous of these reflect major Catholic holy days: the Nativity scene, depicting the birth of Jesus; the Last Supper; and the Crucifixion. All of these scenes have their own intricate iconography. For example, in Nativity scenes, Jesus is attended by an ox and ass -- they are not mention in the Bible, but serve as an iconographical reminder that Jesus' birth is the fulfillment of an Old Testament prophecy found in Isaiah 1:3.

Old Testament Scenes

When scenes from the Old Testament are depicted in Catholic churches, it's usually to presage or reflect the life of Christ. In many churches -- for example, the Arena Chapel in Padua or the Sistine Chapel -- scenes from the Old Testament match up with scenes from Jesus' life in order to add meaning. The Sacrifice of Isaac might be paired with a scene of Christ carrying the cross, for example, underscoring God's divine plan and that God, like Abraham, is willing to sacrifice his own son.

Marian Iconography

The other life cycle depicted in Catholic art is that of Mary. While Mary's life has fewer genre scenes than that of Christ, many are just as important. The Annunciation, the Virgin and Child, and Mary Enthroned are all instantly recognizable to Christians, although their complex iconography is not easily understood by the modern viewer. In scenes of the Annunciation, for instance, a pitcher or vase of lilies represents Mary's purity. There is also usually a light, which is not technically part of the Annunciation, but rather the Incarnation. In some scenes, there's a dove in the light, symbolizing the Holy Spirit. Mary typically kneels at a prie-dieu -- prayer stool -- or holds a Bible in her lap, referencing either Isaiah's prophecy or that Jesus is the "Word made flesh."

Images of Saints

The lives of the saints are an important Catholic subject in the visual arts, particularly in cathedrals dedicated to specific saints. There are literally thousands of saints all over the world, and each has his or her own identifying icons. St. James, for instance, is always depicted with a walking stick, which eventually became an identifier for pilgrims going to his cathedral in Spain. Images of St. Sebastian are easily recognizable, as he is always bound to a stake naked, with arrows sticking out of him. Because some saints, such as St. James, are also Apostles, they are always depicted with a halo.