These are some quotes from some other members on similar topics.

Quote: Spiral architect

Everybody dreams even if they dont realise it.
A dream is a combination of things that has processed in your mid at some time during your life, they are thoughts you have had or things ther you have partaken in. after saying that its is highly unlikely that dreams would have clairvoyant properties. but they are as too say figments of your imagination, and have some link with your memories, wiether your dream is good or bad you have thought of it

Quote: Lilium

People on average dream 4-5 times a night during REM. It's just your mind sorting through your memories of the day you had, as well as messing with some of the older memories you have. It's just that, some people are able to remember their dreams while others can't.

As for my opinion i will say the same as what i have said in related topics.

To have a dream or night mare is your sub-conscious mind falling in and out of sleep while you maybe asleep it doesn't mean your actually fully asleep but when you have a dream or nightmare that means you have drifted right into a heavy sleep you generally experience nightmares or dreams when your sub-conscious mind is waking up which is why you usually wake up not long after having a nightmare or dream, its the brains way of exercising your brain before it is fully operational like warming up an engine.
Its not to be mixed up with astral traveling many ppl believe that they have experienced astral traveling. Astral traveling is when the soul leaves the body and is connected to the body by lets say like an elastic band for example some ppl claim to have seen themselves from above and watch themselves sleeping. When the soul is jerked back into the body by the elastic band you usually experience a jerk which can also be related to the falling dream or feeling when a person feels like they are falling out of a window or off a cliff etc and experience a jerk at the end.This may mean you have been astral traveling. While some ppl believe it many don't, many ppl also believe that that if the connection to your body and soul is broken in any way during astral traveling that your soul and body will be seperated forever which in turn results in your soul finding a new body hence re-incarnation but thats another story for another time.

And i agree with the two previous posts i believe the contents of our dreams are memories and the days happenings and can even be of the last things we see on tv etc

But when i was young i used to have a dream when i would get tickled by a gloved hand that used to come out of nowhere and i wouldn't be able to get away until i would twitch and convulse until i woke up. After that i absolutely hated being tickled and could not stand it so i do think that dreams do affect the real world in some ways. (and it only happened in one house .... maybe it was a spirit i never will find out.)