If you haven’t already grabbed a few modules here’s another intro video from FluxWithIt to tempt you. I never knew HP stood for horizontal pitch.
“This is just simply a primer to get people a little bit of info on what eurorack is. How to get started, and what some of the key elements are.” – fluxwithit.com/intro-to-eurorack-modular/
For more info: wikipedia.org/wiki/Modular_synthesizer