Question about AS1 OOP: Object Basics by Senocular

that is correct. Flash, when tracing movieclips, returns a path to that movieclip as its set within the Flash movie. Because you can load other Movies into Flash with their own _root timelines, Flash defaults each trace path to their respective levels. _level0 represents _root of the main timeline. _level1 would be _root of a swf loaded into level 1.