Over the past decade a significant amount of recommender systems research has demonstrated the benefits of conversational architectures that employ critique-based interfacing (e.g., Show me more like item A, but cheaper). The critiquing phenomenon has attracted great interest in line with the growing need for more sophisticated decision/recommendation support systems to assist online users who are overwhelmed by multiple product alternatives. Originally proposed as a powerful yet practical solution to the preference elicitation problem central to many conversational recommenders, critiquing has proved to be a popular topic in a variety of related areas (e.g., group recommendation, mixed-initiative recommendation, adaptive user interfacing, recommendation explanation). This chapter aims to provide a comprehensive, yet concise, source of reference for researchers and practitioners starting out in this area. Specifically, we present a deliberately non-technical overview of the critiquing research which has been covered in recent years.