  These are lecture notes presented at the online 2020 Hadron Collider Physics
Summer School hosted by Fermilab. These are an extension of lectures presented
at the 2017 and 2018 CTEQ summer schools in arXiv:1709.06195 and still
introduces perturbative QCD and its application to jet substructure from a
bottom-up perspective based on the approximation of QCD as a weakly-coupled,
conformal field theory. With machine learning becoming an increasingly
important tool of particle physics, I discuss its utility exclusively from the
biased view for increasing human knowledge. A simple argument that the
likelihood for quark versus gluon discrimination is infrared and collinear safe
is presented as an example of this approach. End-of-lecture exercises are also
provided.
