I honestly don't believe dreams can foretell the future, and my reasoning behind why it sometimes feels like that is because say something you dreamt comes true in some form or fashion, it's because its a hope or desire. Dreams feed off of feelings, past experiences, as well as knowledge you know. You hope so much for something to happen, you dream of that hope, and not to long after through a series of choices, it may or may not come to pass. That's my say on 'dream foreshadowing'. Even if an event happens exactly like a dream, I still don't believe dreams can foresee the future; it's just coincidence or you made it happen that way.
Personally I feel dreams are technically another version of reality within your mind, only everyone has their own version. How much a dream feels real is by how much you know, and how exact in detail as well as how well at manipulating the five senses it is.
I'll let you on to something-- A majority of my dreams involve me as a fugitive running away from the authorities(yeah, I know- very action filled too), one dream in particular that involved this frequently occurring scenario, I come upon a desert within a dense jungle(yeah, piece that together x'D ). Now, I've never been in a desert or a jungle but I know enough about them. To my feet, the sand felt cold and dry-- but the air hot and humid.
You didn't have to have been to these places to know this, simply studying and knowing key traits about locations and the dreaming brain will do the rest on piecing them together in exotic, unique ways.
Recently, during the Halloween events when I got so little sleep trying to get tokens, I'd often dream I'd still being doing it. As for how real dreams can get, there are times where you'll be half awake and half asleep, I've done this a couple times in the past years, and I find its under certain conditions. If I sleep in a dark room without any source of light or sound, around 2 o'clock in the morning it occurs. I'll give you one of those times under those conditions giving; I sleep oddly, just so you know-- I sleep with my feet at the head of the bed and my head at the foot of the bed. It's really the only way I'll fall asleep-- Anyway- I'm 'wake up' by lifting my head and look around my room to see these miniature, furry dragon-like dragonflies in my room... Now that I think about it, they looked very similar to Glassworks only darker- and I turned my head slowly to the left to see one fly by my head and I lift up my hand to touch it, I appear to miss it but I literally felt something cold and scaly on my fingertips.
Other times this has happened, I'd see shapes and strange creatures within the dark of my room, but this one in particular I recall very vividly. Now that I have a small light source, and some music to play-- I haven't had these happen.
Sometimes when your walking in your dream, you could be sleep walking as well-- As I've had this happen to me when I was little, another incident I remember clearly.
Can't say I've ever had a nightmare, but I've had night terrors which are far worse; I recall having one this year but can't remember exactly what was happening in the dream part of it, other that I woke up suddenly shaking and heart racing.
But yes, I feel the more realistic a dream seems, it is all on how much knowledge/experience you have. Dreams that I recall, I often analysis and in those studies I find this the be very true. I also believe that everything you see in your dreams, you've seen in real life whether it be in a movie, roadtrip, videogame, and so on,(you're brain remembers EVERYTHING you see/touch/taste/hear/smell, even if you can't) or it's bits and pieces of things you've seen combined together to make something seem new-- Though I also believe that the creativity of the brain isn't secluded to only be used when you're awake; meaning, perhaps the brain has taken something you've seen, but has added your own personal touches to it, making it unique only to you.
I've gotten some interesting story ideas from my dreams, and while I can't recall ever seeing such things- either it was something I saw for a moment, and while I can't recall it, my brain remembers seeing it and thus reveals it through dreams. Though, there's the chances your brain combined two or more things together to make something that you never really saw, but through knowledge you know, has made this completely new thing that's new and original. Hence why I say creativity isn't limited to only when you're awake. ;3
Eh, I realize I rambled a lot, but this is my two cents that I'm very much cemented on.