Copyright Laws

First off, I loved the video we watched about copyrights with all the Disney characters! It was a little hard to follow at first but I think it really drove the point home. I learned that their are certain ways that are acceptable to borrow parts of copyrighted material: to teach, news reporting, parody (this was interesting to me, but it makes perfect sense!), and in making critical comments. I want to learn more about copyright laws because even though you can use bits of copyrighted material in certain settings, you still must be careful in how you use it. For example, part of fair use is that you use the copyright in a way that does not change its original meaning (at least I think that is true, the video says you cannot change the commercial impact) but if that is true, wouldn't parody change the meaning because it is making fun of the original work? I'll have to do some more research I guess.