Normally, when you say an atom has a certain charge, you're talking about an ion. Formal charge, however, is a sort of meta number that you can calculate for any atom in a molecule. Although it doesn't represent measurable, actual charge, it can give you an idea as to whether a particular Lewis structure is stable or reasonable.
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)