This review study aims to understand the concept of adults' digital health literacy (DHL), a recently emerging significant concept but still confused. For this, we seek to find the core competencies of digital health literacy by comparing those of existing relevant literacy concepts (i.e., health literacy and digital literacy). We identified seven core competencies of DHL across analytical, context-specific, and socioecological aspects: (a) traditional literacy, (b) information literacy, (c) media literacy, (d) health-related literacy, (e) technology literacy, (f) scientific literacy, and (g) socioecological nature. We also found the shared core aspects among DHL and digital and health literacies. The findings of this study contributed not only to grasping the concept of digital health literacy better but also to providing a fundamental basis for programs to enhance the DHL of adults. This article concludes with discussions about the findings and practical and academic implications.