Iconography in the Greek Orthodox Church
The word "icon" , from the Greek word, "Eikon", meaning "image", is best described as a "symbolic representation having characteristics of the actual subject." These characteristics are manifested in artwork on walls, such as murals and mosaics.
In the Greek Orthodox Church, icons are depicted as symbolic representations of the Holy family, Saints, angels and other key figures that shaped the Church through two millennia. While the human characteristics are captured in the art, added symbolism portrays the spirituality of the subject in the art.
This is seen, for example, in the icon of St. John, wherein angel-like wings are attached to a human-looking figure to depict a higher than human status, as shown in the icon photograph.
To better understand iconography, let's consider a flag. A flag is but a patterned piece of cloth, yet it symbolizes much more to the nation of its citizens. Likewise, an icon's meaning goes beyond the artwork itself. Further, just as a flag is venerated, ie treated with highest respect for what it symbolizes, an icon is not worshipped, but is venerated also.
It is in this context that icons are widely used in the Greek Orthodox Church as symbols and as reminders of events and people who have achieved the highest pinnacle of their faith.