What is the significance of dreams or nightmares?

ever since i was little i always had the most horrific disgusting nightmares, like being d by my biological father [this was when i was 7] lately things like being abducted and taken to a house with my younger sister, having a baby and not knowing what to name her, and doing my best friend?! i couldn't even control the dream its like i was watching us al i could do was slow it down i woke myself up just in time before anything happened idk why but that one scarred me the most out of all of them