A node is a stopping point along a series of branches. A figure such as a humanoid would have each body part as a node for example. These are what you select and move around. Filter Forge uses a node-based editor and each "thing" you add and link together and drag around would be a node.

 

More data at en.wikipedia.org/wiki/Tree_(data_structure)

Reality Plug-in tips for DAZ Studio and other 3D stuff @ TakoYakida World