Since its birth in the aftermath of CERME10, discussions in TWG19 concentrated on identifying its research territory and on creating opportunities for collaboration among the participants beyond the conference sessions. These discussions led to shifting the focus of the group on mathematics teaching and teacher practice (s) and to an initiative of working on shared data that fueled fruitful explorations related to conceptualizations and theorization of mathematics teaching. The participants’ contributions and the work carried out during CERME11 sessions challenged further the core ideas of how mathematics teaching can be defined and studied while an emerging distinction between teaching as an activity and teaching as work stimulated further the group’s discussions.