Icons are didactic in that they teach theology in images and color.” There icons however are much more than pictures — they are sacred images, which convey spiritual truth in picture form, and are sometimes described as windows to heaven.
It is important to understand that icons are not subjects of worship; they are not idols, but aids to worship. All the honor passes to the prototype (i.e. the person depicted by the icon). In other words, someone bowing before an icon of Christ and kissing it is expressing his or her love for the Savior, much as you might kiss a photo of your husband or wife when apart. Icons speak to the Christian spirit as they remind us of God's work in His people in various times and places throughout human history. Icons often adorn areas of prayer.
The faces are not depicted naturally because they are supposed to convey the person as “beyond this world” in the presence of Christ.
Symbolism in IconsThere is a wealth of symbolism in icons. For example, the halo around the head of a Saint denotes the light of Christ shining from within. A blue garment indicates humanity and red indicates divinity. Thus, Christ has a red undergarment and a blue outer garment, because He is divine and put on humanity. Mary, on the other hand, has a blue undergarment and a red outer garment, as she was human but she became divine by bearing Christ.
+ An Introduction to Iconography, The Good Shepherd Orthodox Church, Australia