When authoring a DVD-Video disc using DVD Studio Pro, you have the option to choose the "startup action". This is the function that tells the disc what to do when it's inserted into a DVD player. For example, you might set your startup action to go directly to a main menu, or to display a copyright warning screen.
It's generally wise to set the startup action property when authoring a disc. While the DVD specification allows for a startup action to be undefined, a disc without the startup action property defined requires some action by the user. Most users expect to be presented with a menu or some information when they put a DVD-Video disc into their player. Also, some players may not play discs that don't have a startup action defined.
The Startup Action property is located under the General section of the Property Inspector. For more information, consult the DVD Studio Pro manual.