crib sheet
1. A piece of paper or other document containing information about or the solutions to questions of a test or exam, which may be used for cheating, studying, or by someone grading said exam. Jim was caught using a crib sheet during his test and failed the course as a result. My friend gave me a great crib sheet to use while studying for my final exam.
2. Any document on which complex or difficult information is summarized so as to allow for easy reference and/or understanding. I made a crib sheet of everyday Japanese phrases so I would know how to say at least a few things while in Tokyo next week!