There are two types of dreams. The hopes and wishes we have for our future, and the hallucinations we have while sleeping.
So first off, hallucination dreams. Most of these dreams are really random and might include stuff from that day. I had a dream one time that I went to a festival, the dog from Little House on the Prairie belonged to my Grandma, and my shirtless brother died in my arms. Guess what happened that day? I went to a festival, watched Little House on the Prairie, and I have absolutely no clue where the dying brother thing came from. Sometimes I try to think about something while I'm falling asleep so I can dream about it. This usually doesn't work. It's awesome when you realize your dream is a dream, because you can experiment with life without any damage actually being done. Although it probably wouldn't actually happen that way in real life, it's fun.
Wish dreams are closer to realistic than hallucination dreams. I dream to dance on Broadway someday, and though that probably won't happen, it's still on the list. Some people have dreams that come true because they put hard work toward them instead of just wishing.
Both kinds of dreams tend to be fantasy, but it depends on what you do with your dreams that makes them reality.
-Dakota