A relic is, in the simplest definition, portions of the earthly remains of Saints - also included are pieces of their clothing, vestments, or, for instance pieces of the True Cross. Now, I know that in Catholicism they break it down into First, Second and Third Class relics. A First Class relic is an actual piece of a Saint - a finger bone for instance. A Second Class relic would be a piece of their clothing - something that they used and touched. A Third Class relic would be something that touched something the Saint used. I'm not certain if Orthodoxy classes their relics in the same way, or at all.
In Catholicism, and, I believe, Orthodoxy as well, a relic is embedded in the altar of a church at the consecration of that church.
We venerate the relics of Saints because of the belief that, even after death, their body remains the temple of the Holy Spirit and that God may still perform miracles through their remains. I believe this is tied into the understanding of the physical world. I've heard it described as a 'sacramental world view' - God acts through physical things to affect us. Thus why all of the Sacraments or Mysteries involve not merely words and spiritual effects, but physical objects as well. Water at Baptism. Bread and Wine at Communion.
Go back to my posts on Moses and the Burning Bush or Elisha's Bones. Both contain verses from the Bible briefly illustrating that interaction with God makes physical, worldly things different. Sanctifies them. Elisa was dead and gone, yet touching his bones brought a man back to life. Why? The power of God working through the physical 'medium' if you will, of a saintly man's bones.
Now no ones saying that if you touch a dead person with the bones or a Saint they'll jump right up, all better, but is it so inconceivable that God can still work miracles in this way? Or do you think that the Presence of God, even in the slightest reflection, does not alter a physical form?
So that's my incredibly late and short relics post.
Any one have anything they want to talk about? Questions you're just dying to know the answers to?