Every element of the JavaFX Scene is a part of the large graph (or a tree, strictly speaking) that starts from the root element of the Scene. All these elements are represented by the class Node and its subclasses.
All SceneGraph elements are split into two categories: Node and Parent. Parent is Node as well, but it can have children Node objects. Thus, Node objects are always leaves (endpoints of the SceneGraph), but Parent objects can be both leaves and vertices depending on whether they have children or not.
Parent objects generally have no idea what kind of Node objects their children are. They manage only direct children and delegate all further logic down the graph.
This way, you can build complex interfaces from ...
