Backgrounds: this theoretical article reviews empirically and in detail the concepts of well-being, optimal/positive mental health, types of well-being and flourishing, with a view to clarification and differentiation based on what the current scientific literature offers, and given that they are often used as synonyms, or as interchangeable terms. State of the art: various criteria of inclusion and reference of what we usually consider "positive" and "negative" in scientific studies of well-being and distress (disease, pathogenic, decay) are explained and proposed as a framework and reliable guide for future research and work methodologies related to the constructs studied here, as well as a means of support in the elaboration and enrichment of the same definitions. In addition, specific and differentiated concepts of well-being, optimal mental health and flourishing, which are recogniz...