The world is in the midst of an opioid crisis. Nearly 92,000 persons in the U.S. alone died from illicit drugs and prescription opioids in 2020 [1]. This number does not include the countless other individuals who die as a result of the violent crime that accompanies the illicit drug trade. To address this crisis, we need to appreciate aspects of drug addiction. The goal of this brief review is to highlight some major facets of addiction neurobiology, focused on opioids, to provide a basic understanding of the research and terminology encountered in more detailed in-depth articles and discussions on addiction.