I know little about dreams and their interpretation. Some, I know, have studied them; perhaps most famously, or infamously, Freud and his not entirely faithful student, Jung.
They were of course thought to be a great importance in ancient times, but it's hard for us, now, to see them as divine or demonic visitations or visions of the future. Some of us still do, of course. We never learn, really, regarding certain things; sometimes because we choose not to do so.
I see them as peculiar little snippets of the real or the imagined, mostly disjointed in nature. Mine can be spectacular, in a way, as to their landscapes or dreamscapes. Colossal and complex cities figure often in my dreams, I don't know why. Sometimes I'm lost in them. Sometimes they're background to some purpose of mine or others who vaguely appear and disappear. Sometimes, I can make things happen in them--change the dream, the "location" or set in which they play out, or have the characters do things I want them to do. I know I'm doing that when I do it.
I find it difficult, though, to see them as significant beyond the fact that they can make one feel a particular emotion strongly; too often regret, in my case. They provide me with no special insight into anything, myself included. It seems other animals dream as well, judging from the movements of their bodies while sleeping. It doesn't seem to be something peculiar to we humans. Having them seems not to distinguish us as particularly wise or privileged.
I find it odd that seemingly intelligent people seriously consider the possibility that what we think of as real may, in fact, be a dream. If my own dreams are any indication, the real is nothing at all like a dream. First, I can't control the real as I control a dream (sometimes). More typically, though, dreams are disconnected, may quickly change unexpectedly, involve people dead, are hazy and unclear. They're quite different from the real. so much so it seems fatuous to claim they're similar in any significant sense.
I therefore find arguments that the existence of dreams somehow support skepticism incredible; also arguments that they indicate that our senses are in some way untrustworthy. Dreams are strikingly peculiar. As such, it makes no sense to maintain that we can infer anything from them regarding what is or is not real or whether we can perceive what is real. It makes even less sense to speculate that we're living in a dream, as if we were we certainly would not have the experiences we have. It would have to be a very special kind of dream. One, in fact, which isn't a dream.
Despite this, philosophers have taken such claims seriously. Descartes did, of course. But as he claimed to doubt, or have the capacity to doubt, in philosophy what he so clearly did not and could not doubt in life, it's unsurprising that he would purport to question whether the real is a dream. The kind of "doubt" Descartes claimed to have while philosophizing was a very unreasonable doubt; it required no reason to doubt.
The fact that one doesn't know that one's dreaming is said to support such claims. In fact, that's not always the case, as in so-called "lucid dreams." Otherwise, though, it would seem perfectly reasonable to maintain that we don't know we're dreaming when we dream because we're asleep. Being asleep, we're not as reflective or intelligent as we are when awake. We generally don't know much of anything going on when we're asleep, yet things happen while we are.
It sometimes strikes me that we must purposefully disregard what we know, or at least have no reason to doubt, in order to entertain certain philosophical positions. It takes a real effort to do so in certain cases. Shouldn't this lead us to question the wisdom of these positions? It doesn't seem so.