The ability to explain word meanings is central to a child’s language development and socialisation into different domains of language use. In previous research explanations have been shown to be linked to cognitive and linguistic development as well as academic language and discursive skills. This paper analyses what kinds of linguistic and discursive competences are put to use in explanation activities in interactions between an 8-year-old bilingual child (Albin) and his mother around a digital game. The data comes from a larger data set of video-recordings and field observation of children’s interactions around games. The analysis focuses on explanation sequences in which the child explicates the meaning of objects and procedures in the game world. The analysis shows how explanations are initiated, how they unfold in interaction and how they make relevant asymmetrical roles for the participants, allowing the child to construct a position of knowledge with regard to the game, an important part of his life world. More specifically, the analysis elucidates how Albin’s explanations highlight semantic features and relations that are meaningful for him and how he employs a wide range of linguistic and other semiotic resources in constructing his explanations in a context-sensitive way. The findings shed light on linguistic, interactional and multimodal features of explanations as a discourse activity and provide a window into practices of two-way language socialization in the family.