The Internet has become an important environment in everyday life of children and youth. Consequently, understanding basic Internet concepts has been listed as a target competence in many school curricula. However, any constructive approach to teaching concepts of the Internet should take into account learners’ initial conceptions, shaped by daily experiences, that they bring into the classroom. Based on a systematic literature review of research published between January 2000 and March 2022, we synthesized more than 400 descriptions reported by children and youth and classified them into five categories: (1) the structure of the Internet, (2) responsibility for the operation of the Internet, (3) web search engines and their function, (4) transmission techniques and (5) services of the Internet, as well as into subcategories that encompass commonly found kinds of conceptions within these categories. In addition, we classified all conceptions into three types: (1) intuitive, (2) elaborate and (3) misconception. The results show that children and youth hold more intuitive than elaborate conceptions. They also hold many misconceptions in all five categories. Although it has been suggested that age or user’s online experiences may be important factors for shaping elaborate conceptions about the Internet, we observed that many intuitive conceptions and misconceptions seem to be persistent across different age groups. This indicates that these factors, although necessary, but may not be sufficient for developing adequate conceptions. Instead, we argue that an elaborate conception of the structure of the Internet requires explicit learning and instruction. Finally, we explain implications of our findings for education and for future research.