The gut microbiota are mainly composed of and and are crucial for metabolism and immunity. are a family of bacteria within the order . produce short-chain fatty acids via endogenous (mucin glycans) and exogenous polysaccharides (dietary fibres). The family exhibits a cross-feeding relationship with probiotics, such as and . The alleviating effects of a plant-based diet on inflammatory bowel disease, obesity, and type 2 diabetes are associated with an increased abundance of , a potential probiotic bacterial family. This study reviews the current findings related to and systematically introduces their diversity, metabolism, and function. Additionally, the mechanisms of in the alleviation of chronic diseases and the limitations in this field of research are introduced.