You've done the right thing Carrie. You use iMovie to create your movie, which includes editing clips, and adding transitions, titles, music and effects as desired. The movie you create in iMovie can be uploaded to sites like YouTube and Facebook. It can also be exported for viewing through an Apple TV or other media player connected to a TV.
If you wish to burn your movie to a DVD, that's where you need a separate program, such as iDVD or Toast Titanium. In iDVD you can choose a theme for your DVD, just like those you see on commercial DVDs. The theme will loop (usually for about 30 seconds) until you click on the play button on the DVD player remote. Clicking on Play will cause your movie to start playing. If you inserted chapters in iMovie, these will carry over to iDVD. The DVD menu will show a Scene Selection button. From that button you can select any of your chapters (again, similar to a commercial DVD).
To send your movie from iMovie to iDVD, you have at least 2 options. You can click on the iMovie menu item "Share>iDVD" - this action will open iDVD automatically and insert your movie into a theme and place a button "Play Movie" on the theme. You can choose a different theme if desired. You will also see the Scene Selection button if you've included chapters in your movie.
Another method is to select the iMovie menu item "Share>Media Browser". After the encoding finishes, open iDVD and click on the Media button at the lower right of the iDVD window. Now click on the Movies tab, locate your movie, then drag it to the iDVD theme you've selected. You will then see the Play Movie button and Scene Selection button.
The second option - Share>Media Browser - seems to produce a better quality DVD than when using Share>iDVD, so I prefer to use Share>Media Browser.
If you have any further questions, please come back. But first have a look at the link I provided earlier (Apple's page on iDVD).
John