Once you've put the time and energy into creating a finished movie, you want to save your video project properly so that it will always be accessible. I believe in saving a few different copies of your finished video to ensure that you'll always be able to watch it, no matter how technology changes.
This playable DVD contains an MPEG-2 version of your movie. Though it looks like it's full quality, the video and audio footage has been compressed so that it can fit onto a DVD. If you ever want to re-edit the movie or save it on a medium besides DVD, it'll be helpful to have a full-quality, uncompressed version of your project.
The uncompressed video file will be very large (approximately 1 GB for every five minutes of video), so you'll need an appropriate storage device. For short videos, you can use a data DVD or a USB flash drive. For longer video projects you'll want to store the video on an external hard drive or record it back onto a mini-DV tape.