We deal with components such as the notebook, cells, cell groups, boxes, and even things like options and dynamic values can be thought of as components (they might not actually render as something "visual", but they are still part of the render tree and have a certain lifecycle).
Components rendered during another component's rendering are considered the (rendered) children of that other component, which is called their parent. The set of a component's children, children's children (grand children), etc. is called the component's descendants. The set of a component's parent, parent's parent (grand parent), etc. is called the component's ancestors. The top-level component (which is rendered from code outside any other component and hence doesn't have any parent) is called the root component.
Since Backbone.Model already implements the concept of a model with observable attributes and events, we use it as the base class of Component. The analogy to React's state are Backbone attributes.
Read more about how Reback is used to implement the notebook interface.
Reback also provides some useful developer tools.