Are they a way of working things out in your mind?
Messages?
Just remnants/trash from your life??
I very rarely remember dreams, and even if I do (usually when I've woken up half way through a nightmare), I find they're nonsense, with no real context. Then over the next day or so even that nightmare fades from memory until there is nothing left.
I mean even our dog seems to dream or something, or something like it. He'll start twitching and growling in his sleep, chasing imaginary cats or other dogs?
So I don't put much significance on dreams and I don't know why we have them. However I think
some nightmares may have a demonic origin. I can be having an ordinary dream when it suddenly seems to get hijacked and takes a sinister turn. I'll wake up and there will be a sort of profound "darkness" in the room despite the street lights outside, and a sense of something unpleasant hanging about. There may also be a heavy pressure, and a growling sound, representative of an enemy.
It seems to happen around midnight most of the time. Sometimes there seems to be something floating around the ceiling just on the edge of visibility.
Eventually it eases, although a few "Hail Mary's" in my mind seems to help.
Next morning I'll remember the fact it happened, but I usually can't remember the details of the dream / nightmare itself.
Visions are different - they make sense, and you don't forget them. Sister Lucia, the sole surviving member of the trio at Fatima, didn't start writing her memories down till about 1935, 18 years after the visions themselves. But she could remember word for word what she heard from Mary, and accurately describe what she saw.
You couldn't do that with a dream 18 years later. It would have been forgotten long ago.