Lauren,
The purpose of the Review of Literature is to prove to the judges that you know what you are talking about. It tells them that you did research, and know what that research means. Your R.O.L. should include all relevant information for your topic that is appropriate for your grade level. Some good sources are: en.wikipedia.org;
http://www.google.com; an encyclopedia (I find that the McGraw-Hill Encyclopedia of Science and Technology is very useful, although it can get a bit technical.) You can also ask your librarian where books are that deal with your topic. There are two main rules for the ROL. First, don't put anything in it that you do not understand. This included mathematical equations. (don't include a formula that involves multiplication if you do not know how to multiply.) Secondly, be sure and cite all of your sources. More information on how to do this is available at
http://www.noodletools.com.
Hope that this helps. If you have any other questions, please ask them!