Understanding how to access and manipulate data is essential to use Grasshopper as an effective design tool. We highly recommend looking at additional external resources to help aid your understanding of its nature and techniques to control it.
TU Delft wiki page - Pretty good description of the way grasshopper operates on data and the differences between a visual programming environment and scripting. http://wiki.bk.tudelft.nl/toi-pedia/Template:Grasshopper_Data_Tree_editing Modelab primer files - Grasshopper definitions available for download that outline the functionality of some of the common list and tree manipulation components. http://modelab.nu/?cat=3 Pathmapper Help Thread - Discussion on the grasshopper forum with some very useful images and explanations of how the pathmapper works. http://www.grasshopper3d.com/forum/topics/path-mapper-help-1