Why do we dream....
Sometimes it's because our brain is trying to wrap itself around a new idea, and/or something it doesn't totally understand yet.
Sometimes a dream just seems like a continuation on something that maybe we were doing during the day. Something cool and new, and/or different. (I have often had dreams where I was still playing a game in my sleep, or where I was writing a novel. These days, I might be having a conversation with someone, or even online, lol.)
Sometimes the dream might be a warped version of a thought we were having, either consciously or subconsciously; I think this is because the brain doesn't totally have a grasp on something yet, or hasn't come to a decision about something. Or maybe we just feel unsettled for some other reason about something.
Sometimes symbolism is used... or representation of people. Have you ever dreamed about a person but realized after waking up that it wasn't really a dream about them? Maybe your mind just placed them in a slot because they were on your mind (maybe you dreamed about an ex, or a co-worker; maybe that person just happened to be on your mind so your mind used them in the dream).
I love to have dreams where I'm flying. But the dreams where you're trying to run but don't have control over your feet/legs are never fun; feels like running in molasses. or water; very frustrating.
There are a lot of ways to apply dream "analysis." I think you really just have to be in touch with your inner thoughts. Sometimes the dream helps us figure out what those are. Usually I can figure out what the main components of my dream mean, and how I'm feeling about those. That is, when I can remember my dreams.... lol.