The Properties Tab lists all the attributes of whatever is selected. If an object is selected, the properties tab will show that object's properties:
If a node is selected, you can edit what that node will do. The following is an example with an Animate Node.
Whatever you select, the properties tab will show you the attributes for that object. Clicking simulate on that node (any yellow button) will give you instant feedback on the changes you are making in the properties panel.