What exactly is an algorithm? What do people refer to when they say “my algorithm?” What do Computer Scientists mean when they say “algorithm?” How do we know what an algorithm is doing? This chapter situates the term “algorithm” within the framework of “algorithmic media.” It differentiates “deterministic algorithms,” which are typically explored within computer science, from “opinionated algorithms” which are behind algorithmic media like Instagram and TikTok. This motivates algorithm audit studies, which are key to the chapters that follow.