He was not always like this. Originally named Lucifer, he was created as a holy angel in the ranks of the cherubim and was the highest of all angels. That is until he became arrogant and desired to set himself on a throne above God. Because of his sin God permanently stripped him of his exalted position and cast him down "like lightning from heaven". A third of all the angels chose to follow Satan in his rebellion and they were also cast out of heaven; living now as demons.
Other names for Satan are: Lucifer, which means "the Morning Star," the Devil, which means "slanderer," and Beelzebul, which is derived from Baal-Zebub or "lord of the fly." He is also called the tempter, the evil one, the accuser, the ruler of this world, the god of this age, the prince of the power of the air.