A Rule Node is a point in a pathway that can house a collection of rule lines. Rules Lines within a Rule Node define a True or False result and control the result to take either a Select or Reject branch along the pathway at that point.
Example of Rule Nodes.
A Rule Node can contain single or multiple lines of rules which will always evaluate to a True or False result.
A single Rule Line within a Rule Node.
Multiple rules within a Rule Node.
The Hamburger icon 
adjacent to the Rule Node indicates that it contains multiple rules.