Dreams sometimes seem more real than reality. This may be because there is more in our unconscious mind than there is in our conscious mind. In other words, the brain remembers everything it has even seen and heard, but in any given moment we’re only aware of a small portion of those events.
But we also seem to have access to things we’ve never experienced. Carl Jung called it the “collective unconscious”. In religion it’s called the spiritual realm.
For instance, sometimes we dream of things before they happen. Specific events which could not have been predicted otherwise. Or sometimes the phone rings and it’s the person we were just thinking about. This has been studied and it turns out that it’s more than mere chance. Check out Rupert Sheldrake’s research page (scroll down to “Scientific Papers on Telepathy”).
And then there’s non-locality/entanglement. The phenomenon of one thing effecting something else instantaneously, regardless of distance between them. The unconscious mind is even less understood than this.
We are all connected in a mysterious way. And what we call reality may turn out to be the ultimate illusion.