Remote collaboration systems have become increasingly important in today's society, especially during times where physical distancing is advised . Industry, research and individuals face the challenging task of collaborating and networking over long distances . While video and teleconferencing are already widespread, collaboration systems in augmented, virtual, and mixed reality are still a niche technology . We provide an overview of recent developments of synchronous remote collaboration systems and create a taxonomy by dividing them into three main components that form such systems: Environment, Avatars, and Interaction . A thorough overview of existing systems is given, categorising their main contributions in order to help researchers working in different fields by providing concise information about specific topics such as avatars, virtual environment, visualisation styles and interaction . The focus of this work is clearly on synchronised collaboration from a distance . A total of 82 unique systems for remote collaboration are discussed, including more than 100 publications and 25 commercial systems.