  In this chapter, we trace the path from the Tamari lattice, via lattice
congruences of the weak order, to the definition of Cambrian lattices in the
context of finite Coxeter groups, and onward to the construction of Cambrian
fans. We then present sortable elements, the key combinatorial tool for
studying Cambrian lattices and fans. The chapter concludes with a brief
description of the applications of Cambrian lattices and sortable elements to
Coxeter-Catalan combinatorics and to cluster algebras.
