A node is the main element of the deployment diagram. It is a physical element that represents a processing resource, a real physical unit, or physical location of a deployment (computer, printer, or other hardware units).
In UML, a node is defined as Type or Instance. This allows you to define for example 'BackupMachine' as node Type, and 'Server:BackupMachine' as Instance. As a matter of simplification, PowerDesigner handles only one element, called node, which actually represents a node instance. If you need to designate the type, you can use a stereotype for example.
The symbol of a node is a cube:
A node cannot contain another node, however it can contain component instances and file objects: the software component instances and/or associated file objects that are executed within the nodes. You can use shortcuts of component as well.
You can add a component instance from the node property sheet. You can display the list of component instances in the node symbol as well, by selecting the option Components in the node display preferences.