What is that we actually DREAM?

We all DREAM.... this is a fact but what we dream concerns here.

Why is that in a dream we always see ourselfs in first person?
Why is that sometimes it's difficult to recollect a dream?
Why is that we never die in adream rather fall a lot?
Why do we get out of a dream when we have a sensation of falling?
How is that one who has never sensed falling is able to do so in dreams?
Why is it that certain incidents in our life feel like it has occured sometime before and it happening as if we know its consequence?
And many more......

Now the thoughts that have come to my mind is that whether these dreams are some sort chemical activity or are these actually some possible visions of future or are we getting the visions of infinite number of parallel me exisiting in infinite number of parallel universe!!!!!

Do we have an answer to some of these things.

I would really appreciate a lot of views from people regarding DREAMs or any thing related to such happenings to be shared and commented for better understanding....