The Attributes Panel is the main user interface of the Active Node. This panel is updated when the active node changes.
When a node is set as Active, the Control Panel is updated. The Attributes Panel of the previous Active node is removed, and the Attributes Panel of the new Active node is added.
If there is no Active node in the Node Graph, then there is no Attributes Panel to show.
The Attributes Node has widgets for all the Attributes of the node, and it can also have widgets for editing the node data.