As digitization progresses, citizens, patients and providers increasingly encounter digital or hybrid prevention or care services and digitally supported health information. Under these circumstances, electronic health literacy (eHL) as an extension of health literacy (HL) is a crucial skill that entails searching, finding, understanding, evaluating and applying health information based on digital sources when encountering challenges to health. There are currently multiple definitions that do not take into account newer digital applications in particular. The aim of part I of this article by the members of the Digital Health working group of the German Network for Health Services Research (DNVF) is to derive a working definition of eHL which is founded on known definitions of (e-)health literacy and on dimensions of relevant framework models and theories. Particular attention is paid to the delimitation and similarities between HL and eHL. Also, this article looks at the operationalization of eHL in the context of internationally proven approaches. Here, eHL is viewed as a relational construct that can be approached via multidimensional operationalization at the individual, interaction-related and system levels.