In addition to probiotics and prebiotics, the term “postbiotics” has been increasingly used in recent years. Postbiotics consist of non-living microorganisms or their components. They are defined as “a preparation of non-living microorganisms and/or their components that confer a health benefit to the host.” There are numerous classifications of postbiotics, which are determined by their chemical composition, physical form and function. The most common classification is based on the metabolites produced by the microbiota. Research has shown that postbiotics possess antioxidant, immunomodulatory, antiproliferative and antibacterial properties. Due to their numerous health benefits, postbiotics have become increasingly popular on the market in recent years. This review includes the concept and classification of postbiotics described in the literature, their mechanisms of action, as well as their impact on the microbiome, and the possibility and benefits of their application in the food and pharmaceutical industries. The use of postbiotics has great potential in promoting health improvement, however more extensive research needs to be carried out.