If you're talking about rendering the timeline, it's just a way of giving you a clean preview of your project in progress. Especially if you're using mixed media, adding effects and using photos and graphics, rendering regularly can keep your project running smooth and looking good.
It has nothing to do with the finished project though. It's just for giving you a good, clean playback of your timeline.
And, yes, you can certainly continue to make changes. When you do, just render your timeline again. (You'll only need to re-render the parts you changed.)