The article addresses frequently asked questions (FAQs) about the International Scientific Association of Probiotics and Prebiotics (ISAPP) definition of postbiotics, which are defined as "a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host." The authors, Gabriel Vinderola, Mary Ellen Sanders, Marla Cunningham, and Colin Hill, explain the rationale, scope, wording, composition, and commercial implementation of the definition, as well as the expected standards for safety, efficacy, quantification, and mechanisms of action. They emphasize the importance of a clear and precise definition to avoid confusion and promote innovation in the field. The article also discusses the use of metabolites in postbiotic preparations, the role of inanimate cells, and the need for deliberate inactivation processes. It highlights the importance of characterizing and quantifying postbiotic preparations and the necessity of demonstrating safety and efficacy through well-designed clinical trials. The authors conclude by noting that the ISAPP definition aims to provide a common language for research, consumer products, and regulatory actions, and they welcome ongoing discussions and debates in this rapidly evolving field.The article addresses frequently asked questions (FAQs) about the International Scientific Association of Probiotics and Prebiotics (ISAPP) definition of postbiotics, which are defined as "a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host." The authors, Gabriel Vinderola, Mary Ellen Sanders, Marla Cunningham, and Colin Hill, explain the rationale, scope, wording, composition, and commercial implementation of the definition, as well as the expected standards for safety, efficacy, quantification, and mechanisms of action. They emphasize the importance of a clear and precise definition to avoid confusion and promote innovation in the field. The article also discusses the use of metabolites in postbiotic preparations, the role of inanimate cells, and the need for deliberate inactivation processes. It highlights the importance of characterizing and quantifying postbiotic preparations and the necessity of demonstrating safety and efficacy through well-designed clinical trials. The authors conclude by noting that the ISAPP definition aims to provide a common language for research, consumer products, and regulatory actions, and they welcome ongoing discussions and debates in this rapidly evolving field.