The definition to the Scrum Master is described in the Scrum Guide of Scrum.org with a few lines: "The Scrum Master is responsible for the understanding and the implementation of Scrum. He does this by ensuring that the Scrum team adheres to the theory, practices and rules of Scrum. The Scrum Master is a Servant Leader for the Scrum Team. The Scrum Master helps those who are not part of the Scrum team to understand which of their interactions with the team are helpful and which are not. The Scrum Master helps to optimize the collaboration so that the value generated by the Scrum Team is maximized". (scrum.org)

But what does this mean for the everyday life of a Scrum Masters?
A Scrum Master must fulfil a wide range of tasks from moderator, rule holder to coach. The easiest thing to do is to use the Rule Einhalter. With the Scrum Guide the rules are fixed and can be easily applied. It becomes more difficult with the moderator. Meetings must be moderated and retrospectives prepared in such a way that a good result is achieved. This requires techniques and knowledge of human nature that help the Scrum Master to build up a good relationship of trust.
It is most challenging for the Scrum Master as a coach. The team must be supported in such a way that solutions can be worked out, but also conflicts can be solved.

What else does a Scrum Master have to do for you?