To me, dreams are our visits to the astral plane while our body rests. We play out scenarios to learn, review or try to make sense of situations, but also we simply play around with other souls, whether incarnate or not. I have periods where I don't remember dreams (probably because there's nothing to be found there, or I'm just too tired) and periods where I remember them all, but I only note down the ones I feel are very significant or have something particularly funny, scary or weird happening.
I used to think that it was just "from the brain", because I was raised by an atheist mother who isn't much spiritual (now she's more open to this, but in my childhood, she wasn't), although I always suspected that the places we go to have an existence of their own, and that we meet people in these dreams, not just "avatars" of ourselves. I thought like this until I had a very vivid dream a year ago or so, the most vivid dream of my life, with somebody deceased who had sorta been in the back of my mind until I had sudden thoughts that were out of character for me to have, and wanted to get rid of them through lucid dreaming and then move on. I didn't lucid dream that night, but in the morning, bam. Most vivid dream of my life. I didn't see it coming at all.
That one definitely changed how I saw the whole dream thing. It was so intensely real. Everything felt as if my senses were hyper-hyper sensitive but not overstimulating, it was weird. I could feel every detail of her, as if she was really there, and the feeling is still with me today. It's insanely precious to me. It changed my creativity like crazy. Since then I've not just been over 9000 brimming with creativity, I've also changed as a person. I feel like there was a pre- and post- this dream (and spirit). We didn't cross paths in this lifetime (language barrier and age would've been an issue, as she died when I was a kid), but still... it was real. I've had other extremely vivid dreams that looked exactly like "reality", except there were dead people in them and of course, it didn't behave logically like in waking life, but it was still so realistic I could've sworn it happened in the physical.
I realized you can't invent someone's vibe, especially someone you didn't know physically. It feels like them, and you don't find it with anyone else that you may know. It's their unique signature. My best friend is much more "down-to-earth" and "scientifically-minded" than I am, but she recently told me "it's like touching the person's soul" when you see them in a dream. It's true. It does feel like touching a person's soul. I also noticed I accurately picture people in my dreams: a handful of times I dreamt of my online friends without knowing their height. The first time I dreamt of my best friend, I didn't know she was actually taller than me. It was at the beginning of our friendship. I thought that maybe it was dream physics that made her look tall, since people in her country aren't that tall, but turns out, she is in fact tall... With another, I pictured him about 172-75cm tall, turns out, that's his real height... and I had no way to know, as I didn't see pictures of him that could've given out his height. Either I'm a goddamn psychic or I'm onto something.
I'm not the only one whose life was changed by a dream, and I think that if people dared look at them in a different way than "oh lolz its ur brain", a lot of them would find a lot of meaning there, and possibly be happier, or at least have a less limited and pessimistic view of life. Sure, I still do struggle with bouts of depression, feeling worthy of love and all, but... something in me has changed since I had that dream and I can't "unsee" it. Likewise recently I had a dream that inspires me to write something. My dreams are very important to me. I kinda want to train myself to lucid dream, so I can choose where to go, but every time I went lucid I noticed I had trouble moving or I just got so excited I woke myself up. Shared dreams are also a thing, although rarely reported. Again, I think that if people were more open about it, it'd have a bit more coverage. I could go on and on about dreams, my post is already getting too long, but hopefully this answers your question.