Question....

I am doing a project and I need to know why we have dreams, exactly... can someone help me with this?

Caroline, that is the $64,000 question.

Nobody really knows why we dream. There has been tons of research looking into it for the last few hundred years and people have been asking the same question for thousands of years.

Sorry I cannot be of any more help :(

In short. Very short :
The general consensus is for our brains to disipher the content that it considers necessary through out the day. :P

Check out the the Lucidity Institute.