This book provides an introduction and overview of the growing area of chip-firing. It offers an appreciation for the richness and diversity of chip-firing. Chip-firing refers to a discrete dynamical system -- a commodity is exchanged between sites of a network according to very simple local rules. Although governed by local rules, the long-term global behavior of the system reveals fascinating properties. Working over the simplest type of network, basic properties are covered from a variety of perspectives. This gives the reader both a broad context of the field and concrete entry points...