In its initial incarnation, the Lightning Component framework used the Aura programming framework. This framework was created by Salesforce to handle many of the generic programming needs of web developers at the time. Since then, technologies and standards applied in modern web browsers have moved on and much of what Aura provided has now been effectively absorbed by the latest browser runtimes. Salesforce has taken a fresh look at modern web programming and has determined that a revised framework was required. The result, the Lightning Web Component (LWC) framework, is something that embraces more ubiquitous programming standards and tools (and thus more access to developer skills when hiring), while also resulting in a more performant rendering of components as the browser runtime is more optimized.  

Salesforce uses the term Lightning Component when referring to a component's usage regardless of the programming framework used to develop it. This is useful when it comes to talking generally about how components fit into the general platform programming model and features since they have strived to ensure both types of components can co-exist to help developers incrementally adopt the new programming model. The terms Lightning Aura Component and LWC are used to refer to the old and new programming models, respectively. This book follows the same convention.