Why do we dream?

This is a question which keeps rising now and then within myself,
I surfed to know why actually do we dream,
I learned that dream is an involuntary series of visual or emotional thoughts occurring in the mind during sleep-like state,which simply means u never stop thinking even during asleep, you don't know what exactly are you thinking during asleep unless u dream.

Research reveals that dream is associated with REM sleep. waves given out by the brain during sleep are large and faster during REM. Most adults dream 5 to 6 times in one night. They occur every 90 to 100 minutes and last 5-10minutes.

The pathways of the nerve impulses from the brain to the muscles are blocked, therefore body doesn't move during dreams.

This is all i read about why we actually dream.

I have recently dreamt something very different and odd, which was more like a dream in dream. The research says that its because of the emotional thoughts occurring while someone is asleep, does that really mean am creative in dreaming as well? sounds nice though ;).

My brain never stops raising questions, I still have too many questions as in,

If its really that every adult dreams about 5 to 6 times in one night,
why is that we remember only a few dreams very accurately?
Either we shouldn't remember any of them or we should remember them all.

Its said that the body parts doesn't move during your dreams, but i have seen my mom complaining almost every morning that i talk during asleep or sometimes i had even punched her arm while i dreamt up. Does that mean the nerves from my hand aren't connected to the brain? :|

This study has not brought much of the information which i wanted.

Search continues.......