This video covers Packed Primitives in Houdini 13 and their usage in Instancing. This video is a more detailed explanation of a topic that is covered in brief in the Floating Islands training series.
Packed Primitives are a new form of geometry type that was introduced in Houdini 13. You can think of them as proxies. This video covers the various ways in which you can create them and use them for large scale instancing.