nightmares?

What's the deal with nightmares? I did a search and based on what popped up it looks like as people detox they have nightmares, but i also read nightmares are also your subconscious trying to get your attention about something. what does everyone think? I rarely have nightmares (couple times a year) but when i do, i rarely remember them, but just wake up terrified. so scared that i can't even move to turn on the light, so instead I stay as still as possible and say the Our Father till i fall back asleep (even though i'm not really religious) Last night i had one, and can't really remember what happened except that i was overwhelmed by something, like some kind of energy force and then i woke up very abruptly scared sh*tless. Anyone have any opinions?