Pull up at an intersection, a red truck screeches to a halt at a red light. I think "whoa, deja vu"
But I think -
I have been at that stop light before.
I have seen a red truck before.
I have seen someone screech to a halt before.
My mind accesses all those separate points and constructs what I just saw, based on unrelated bits.
That's how I think Deja Vu happens. Or, maybe I have seen a red truck screech to a halt at that very intersection 30 years ago just like that and never remembered it. Maybe even when I was like 3 years old or something. Who knows?
It's probably also some kind of messenger that I don't think to try and interpret, and probably lose the train of thought that was interrupted by the deja vu, which the messenger would be speaking about.
I also think the dreams and memories that we can't seem to shake are messages that we are intended to interpret once we ever learn how.
2 cents is about all I have on deja vu. It certainly is fun though.