Think of something like a Point and Polyline Feature Class, one representing valves, the other pipes from a pipeline. You add them to a "Geometric Network", and than start editing the network. You move the valve (original Point Feature Class), and the attached Pipes move with it. Or you determine which endpoints in the utility network will be affected by shutting down this valve.
This kind of "behavior" requires all kinds of relationships and constraints in the DBMS and in ArcMap to be maintained automatically. That is "behavior" in the context of geodatabases. You don't really "set it", you create it automatically once you define and start using those special complex datatypes like Geometric Networks, Network Datasets, Parcel Fabrics and so on...
