An Introduction to the Lattice of Torsion Classes

In this expository note, I present some of the key features of the lattice of torsion classes of a finite-dimensional algebra, focussing in particular on its complete semidistributivity and consequences thereof. This is intended to serve as an introduction to recent work by Barnard–Carroll–Zhu and Demonet–Iyama–Reading–Reiten–Thomas.