Some Components take an input node set, apply some processing and output the modified node set, however the structure of the input and output data remains the same.
Examples of such components include Filter, Sort, First, Last, GetAt etc.
In the diagram above we can see that the "Filter" component takes its nodes from the XML Reader->sports_club->club->member. At the point when the Filter->Nodes connection point input is connected the filters output connection point is created this takes its type from the Filter->Nodes input and so is of type "'member".
Typically any further processing is now performed against the output of the Filter component.