When we're considering the security properties of something, whether it's a building, an app, an API, a network, or really anything else, there is a core set of concepts that we lean on to inform our evaluation. These core concepts provide a foundation to reason about whether the security provided by the entity in question is sufficient and, in the case that it's not, how you can mitigate the risks posed by its flaws. In this first episode on core security concepts we discuss authentication vs. authorization, the principle of least privilege, some flaws of human behavior, security vs. usability, and the elusive notion of perfect security. With these concepts in hand you will be better equipped to consider the risks of everything you interact with in your day-to-day life.