What Is Free About Free Model

Background # I was trying to get an overview of algebraic effect, and I found the famous paper “What is algebraic about algebraic effects and handlers?”. After reading it thoroughly I felt like grasping the main idea, however, left with some details haunting me. And they really prevent me from digging into practical proofs and construction, which further prevents me from understanding another paper namely “Algebraic Effects Meet Hoare Logic in Cubical Agda” which initially ignites my interest in algebraic effect.