A dæmon is a supernatural immortal creature which is an enemy of God and totally evil. Dæmons may also be referred to as 'devils,' with a lowercase initial letter to differentiate them from the Devil, a title for Satan. A succubus is an example of one kind of dæmon.
More liberal-leaning Protestants tend to either ignore or explicitly reject the existence of dæmons, or view scriptural passages about them as metaphorical for sin or illness. The Catholic Church still claims demons exist and actively try to corrupt humans into sinful behavior, but has reduced the significance of this element of doctrine.
More conservative Protestants, especially those from evangelical denominations, see dæmons as engaging in a constant struggle for the soul of each person. Fallen angels who followed Satan in his rebellion, dæmons are believed to operate in secret in order to corrupt and influence individual humans in order to ensure they turn away from Christ.