Satan:
from:-
http://www.goarch.org/en/ourfaith/articles/article7079.asp
The devil was created by God as an angel, who was free, and as a free agent chose to oppose the plan of God. That is, the devil is a fallen angel. Satan is not evil by nature, but by will and action. In Satan there is no truth whatsoever; he is absolute falsehood and deception. Satan is not just a negation or deprivation of good, but a positive force with free will that always chooses evil. The devil has the ability to recognize divine power, as in the incident of recognizing Christ as the Son of God (Matt. 4:1-11; Luke 4:1-3). Satan has under his leadership legions and invisible powers, with their own "satanic teachings." The devil and evil spirits know that God exists and recognize true and devoted Christians, but pious Christians discern the plans of the devil. The devil, however, constantly employs every method of deception to enslave man to satanic forces and causes rebellion against God. He is the cause of corruption and disorder, a parasitic power in the world that will ultimately be destroyed by the power of God in the "last days." Because there is no compromise between God and the devil, the struggle will continue until the end.
Lucifer
from:-http://www.newadvent.org/cathen/09410a.htm
The name
Lucifer originally denotes the planet Venus, emphasizing its brilliance. The
Vulgate employs the word also for "the light of the morning" (Job 11:17), "the signs of the zodiac" (Job 38:32), and "the aurora" (
Psalm 109:3). Metaphorically, the word is applied to the King of Babylon (Isaiah 14:12) as preeminent among the princes of his time; to the
high priest Simon son of Onias (Ecclesiasticus 50:6), for his surpassing virtue, to the glory of heaven (Apocalypse 2:28), by reason of its excellency; finally to
Jesus Christ himself (II Petr. 1:19; Apocalypse 22:16; the "Exultet" of Holy Saturday) the true light of our spiritual life. The Syriac version and the version of Aquila derive the Hebrew noun
helel from the verb
yalal, "to lament";
St. Jerome agrees with them (
In Isaiah 1:14), and makes Lucifer the name of the principal
fallen angel who must lament the loss of his original glory bright as the morning star. In
Christian tradition this meaning of Lucifer has prevailed; the
Fathers maintain that Lucifer is not the proper name of the
devil, but denotes only the state from which he has fallen (Petavius,
De Angelis, III, iii, 4).