No problem. Let me see if I can help clear this up. When you start a PrEl project you add some basic ingredients such as movie clips or maybe still pictures. Then you spice this up with some transitions, effects, keyframing, slow-mo, volume adjustments, etc. When you're all finished you create a finished movie from this that may be burned as a DVD, or it can be output to a video file through File>Export>Movie. There are quite a few of these different output types, even including things like Flash movies for web site use.
Whatever type of output you choose, once you've used your PrEl project to create a finished product movie file of some type, that file doesn't contain any of the information from the PrEl project any longer. It's just a movie. It's like a chef baking cookies. Once he's mixed all of the ingredients together and made the dough he can't go back and work with the individual ingredients anymore. The only difference is that with PrEl you can go back into the original project if you like, make changes and adjustments, and output a new version of that movie.
So the idea is that so long as you keep things within the PrEl project realm you are free to do whatever you want regarding all the "ingredients." But once you output it as a finished movie, that movie no long contains those properties that we have been talking about.