One of the members of the Scrum team. His goal is to introduce the Scrum framework to his teams, but also to spread and understand agility elsewhere in the company. Some of his responsibilities include training team members, removing obstacles in the team’s work, and facilitating team ceremonies.
The goal of the Scrum Master is, among other things, to make the team not only change processes, but also change the company culture. They try to create so-called self-organizing teams and become more expendable for the teams over time. This will allow him to help with the change of functioning in other teams.
A detailed definition of the role of the Scrum Master can be found in the publication Scrum Guide.